I've played the post-game extensively and based on my experience I noticed some things that could make the post-game experience a little less tedious for new players and maybe even for some completionists. -Deathtamoor
Try to finish most of the quests between 1 and 38 before you beat the game. Most of them are easy so they shouldn't give you much trouble. You can leave quests #11, #20, #22, #27, and #34 for the post-game because the items required for those quests become easier to obtain later. Do quests #103, #105, and #107 sooner than later. They can still be done later when you are more powerful, it's just these quests may become more tedious.
You should use the grottoes for most of your grinding. Reach level 65 with your Hero by fighting Liquid Metal Slimes in Bowhole or Slimehill after you beat the game. Then focus on grottoes. Keep repeating your highest level grotto until you get a floor with King Metal Slimes. KMS appear in Fire, Water, and Cave grottoes. Once you find a floor with KMS, make a note of which grotto it is and grind here until you can revocate once and get to Lv99 for your Hero in the same vocation. Once that is taken care of you can look for grottoes that have Platinum King Jewels. Platinum King Jewel appear in Ice and Ruins grottoes. Keep repeating your highest level grotto until you get a floor with Platinum King Jewel. Make a note of this grotto so you can come back later. You will want to at least get your Hero to be +3 and Lv 99 in the same vocation. You can keep grinding after you achieve this if you want. I suggest revocating at least once for each job so you can get the special accessories associated with each job. Split the jobs evenly among your party.
Money - Part 1:
You will need a bit of cash to get some of the better equipment from the shops. I suggest using the Ear Cosy Alchemy strategy to make your money. Upgrade one weapon for each of your party members from either Stornway's new shops or the secret shop in Dourbridge. Get everyone some better armour as well. You don't need to worry about alchemy just yet for better equipment. I'll return to the money section later...
Highly Recommended Skillsets: Shield Skill 100 for everyone, Virtue 100 (Paladin) for everyone, Sword Skill 100 for at least 2 people, everyone should have 100 in either Axe or Spears (Spears are better IMO) so you can have Hatchet Man and Thunder Thrust for MKS/Platinum King Jewel hunting. For now I would suggest having two high level Gladiators and two high level Sages. Once you get stronger and can get by with just one Sage, have the other Sage grind in the Gladiator or Paladin vocation. Use most of your skill points in the vocation oriented skillsets e.g. Courage for the stat gains. For weapons, I'd first max out Swords, Fans and then Spears. You can do whatever you want with the remainder of points.
Scrolls: Secrets of the Shield scroll should go onto your Sage that is your main healer so he/she can be immune to critical hits and also give him/her Armamentalist Album. Place Priest's Primer and Minstrel's Manual on your other Sage (or later: Gladiator/Paladin). Place Gladiator's Guide on one of your main attackers and Warrior's Workbook on the other Gladiator.
Some optional scrolls: Place Luminary's Lore on your character with the highest agility and Thief's Theory on your character with the highest deftness. Sage's Scripture can either go on a your main healer (Sage) or your character who acts as a debuffer such as the Mage or Armamentalist.
Other Items: Give everyone at least one Yggdrasil Leaf in their inventories.
Suggested weapons: Falcon Blades for all your sword users which can be bought from Stornway. They don't need to be Über Falcon Blades at the beginning but you should upgrade them to Über using alchemy once you get the chance. Demon Spear for all of your Spear users (also bought in Stornway) until you get a Hero Spear or the Metal Spears from the treasure chests. Your choice for everything else.
Suggested Accessory: Goddess Ring for everyone. Alchemize a Goddess Ring (Life Ring, Sainted Soma and Gold Bar) for each of your characters. You will gain MP with each step and you'll never need to worry about running out of MP while you are grinding in grottoes.
Every time you fight a new grotto boss, make a note for where you fought him. Do this for all 12 grotto bosses. This will come in handy for the DLC quests and if you are interested in using the Hoimi table to get the 2% drops from them. Keep the low level grottoes that have different grotto bosses so your trip to the boss will be shorter should you ever need to revisit. If you find yourself in a new grotto and it's a low level one and it's the same grotto boss that you've already documented, then feel free to delete it after you complete it.
Search for S Rank Enemies in Grottoes:
In order to complete all of the DLC quests you will need access to S rank enemies of every element (Ruins, Cave, Ice, Water, Fire). Another advantage to getting all S rank enemy grottoes is that they tend to have better treasures within. Simply keep completing your highest level grotto until you get S rank enemies for each element. Here is a list of the S rank enemies for each element:
Caves: Wonder Wyrtle, Widow's Pique
Ruins: AU-1000, Void Droid, Platinum King Jewel
Ice: Blight Knight, Platinum King Jewel, Boogie Manguini
Water: Pale Wale, Seavern, Gem Slime
Fire: Vermil Lion, Master Moosifer
I was able to get S rank enemies for each element with a Lv99 +3 Hero. You shouldn't need to revocate more than that. Don't forget to make a note of all your grottoes with S rank enemies, even if you have more than one!
You may be wondering which Mini Medal items are worth purchasing. It really depends on where you are in your post-game. Early in the post-game you should buy some Prayer Rings because they are a useful ingredient for many accessories. 10 of them should be good for a while. Saint's Ashes are useful to make Lucky Pendants which are needed for Monarchic Marks. Monarchic Marks are used in lots of recipes so you may want to buy a few Saint's Ashes early on but not too many because you'll be finding lots of them in the blue chests. If you are a completionist you will probably want to buy lots of Reset Stones since you'll need quite a few of them but only buy them when you don't need anymore Prayer Rings or Saint's Ashes. Buy Elfin Elixers only if you want to use a magic based strategy for the Legacy Bosses. You don't need them for anything else. Orichalcum and Pixie Boots are too expensive and not worth buying.
Blue Chest Farming:
The only Blue Chests that should be of interest to you are ranks E or higher. Here is how you can tell the difference between each rank:
Rank E: Panacea, Narspicious, Finessence, Aggressence, Brouhaha Boomstick, Thug's Mug, Maid's Mop, Muscle Belt, Maid Outfit, Dangerous Bustier**, Toughie Trousers, or Thug Boots.
Rank D: Mystifying Mixture, Hela's Hammer, Demon Whip, Oh-no Bow, Hades' Helm, Riotous Wristbands, Fingerless Gloves, Veteran's Gloves, Blessed Boots, or Skull Ring.
Rank C: 880 gold, Lucida Shard, Perfect Panacea, Unhappy Hat, Depressing Shoes, Ruinous Shield, Skull Helm, Veteran's Armour, Divine Dress, Matador's Gloves, Trinity Tights, Veteran's Boots, Combat Boots, Spellspadrilles, or She-mage Shoes.
Rank B: 1500 gold, Enchanted Stone, Pruning Knife, Hero Spear, Heavy Hatchet, Megaton Hammer, Beast Claws, Wizardly Whip, Attribeauty, Pentarang, or Wyrmwand.
Rank A: 3000 gold, Ethereal Stone, Reckless Necklace, all Metal Slime gear.
Rank S: Sainted Soma, Reset Stone, Yggdrasil Leaf, Stardust Sword, Deft Dagger, Poker, Bad Axe, Groundbreaker, Knockout Rod, Dragonlord Claws, Gringham Whip, Angel's Bow, Critical Fan, Meteorang, Bright Staff. Also, if you are in a grotto with S rank enemies and you find a chest with an Evac-u-bell, there is fairly high chance that it is an S rank chest, so keep that in mind.
Where to farm? I suggest farming in a grotto that has S rank enemies because you have a good chance of getting S rank chests. Farm in a place that has at least two S rank chests, preferably not in a Ruins grotto. Ruins grottos can be annoying because they have too many narrow passageways and it can take you longer to get through the grotto. Be smart about how you farm. Let's say you are on B10 and you have farmed an assortment of E-S rank chests, including three S rank chests and all that's left on floors B11 to B15 is an A rank and some B rank chests. If you already have all of your Metal Slime gear, don't bother with the rest of the floors and just cast Evac after you get your last S rank chest on B10. Once you exit, close your map, reopen it again and continue farming. Even if you don't have access to the Kawasaki Locker you should be able to farm every rare item in the blue chests if you picked a good grotto and are dedicated. Only farm in high quality grottoes. Don't bother farming in a grotto that doesn't even have an A rank chest.
**= The Dangerous Bustier is required for Quest #124. If you want to fill out the Alchemy spots for the Bustier equipment, without having to find another Dangerous Buster then alchemize the Dangerous Bustier into the Silk Buster. Next, alchemize the Silk Buster into the Divine Bustier. Finally, alchemize a Reset Stone with the Divine Bustier to get the Dangerous Bustier once again. Now give this Bustier to the granny in Stornway to complete the quest.
Money - Part 2:
In post-game you will be spending most of your money on Chronocrystals so you can alchemize Agates of Evolution. You can never have enough of them. But what you don't need to do is Gold Armor alchemy strategy. It's not necessary. You should have a heap of cash from all the grinding you did from before but if you have been treasure farming, then you should have enough money after every few runs to buy a new Chronocrystal. Not only do you get money from the Blue Chests but you can also sell the items and equipment you find. If you have more than 4 of any piece of equipment, sell it. Be sure to also sell Gold Bars, Orichalcum (if you don't need any more), Reset Stones (ditto), all of your Gleeban pieces, Densinium, and Mythril Ore. You'll be surprised at how much money you'll get in return. If you still find that you need more cash than you are generating in your treasure hunts, then go to either a Ruins or Water grotto and defeat Gem Slimes for a while.
Agates of Evolution:
Your blue chest farming isn't over once you have all the Metal Slime gear and S rank weapons, you can still farm in same spot for Agate of Evolution ingredients. Agate of Evolution is one of the most important alchemy ingredients but it is also the most cumbersome to make. First off, it will cost you 50,000 gold to make one because until Quest #173 is released on WiFi, Chronocrystals can only be bought in the cave at Lonely Coast. Here's the good news: the rest of the ingredients can be farmed from blue treasure chests in high quality grottoes. Here are the ingredients and in which ranked chest they can be found:
Sainted Soma = S rank chest
Ethereal Stone = A rank chest
Lucida Shard = B rank chest
Astral Plume = D and B rank chests
Sage's Elixer = D, C, B, and A rank chests
Enchanted Stone = B rank chest
Perfect Panacea = C rank chest
Narspicious = E rank chest
If you need more Lucida shards, you can get Evencloth and Brighten Rocks from the Gleeba, Ondor Cliffs, and Upover spawn points. Alternatively, you can also steal Evencloth from Ragged Reapers near Zere and Brighten Rocks from Goodybags in the Bowhole. If everyone in your party has Half-Inch learned and you all have decent Deftness stat boosts from vocation skills, then you are better off stealing. Also, if you are running low on Astral Plumes you can steal Fresh Water from Cheeky Tikis in Gerzuun and Flurry Feathers from Weaken Beakons in the Bad Cave. Don't bother with the Fresh Water and Flurry Feather spawn points, it's not worth the trip.
Masayuki and Kawasaki maps do make grinding and farming easier but they aren't necessary if you are a completionist. First off, you don't need to max out your Hero to Lv.99 +10 to get some really good quality maps. Lv.99 +3 is good enough. Also, with a little time and patience you should be able to get all of the S rank weapons and then some without having to resort to timer manipulation in the Kawasaki Locker. If you pick a good quality grotto to farm in (the shorter the distance, the better) then you should have everything you need in a few days and you'll be farming for Agate of Evolution ingredients on the side as well. Hoimi table manipulation however, is a definite must. 2% drops from the 12 grotto bosses will drive you insane if you try to do it the normal way, especially if you want more than one item. For completionists: Don't use the Hoimi table the first time you get a chance for an Alchemiracle item. You will want to use a Reset Stone on that item so you can fill out a slot in your Alchenomicon. After that slot is filled, always use the Hoimi table for Alchemiracle attempts.