Here you can find useful pieces of information that the game ever tells you.
Tips and Tricks
Once you’ve accumulated enough points to pass a floor or stage, you can do so by selecting the Sacred Tome (Zetta) on the battlefield and then selecting the “End Action” option. This option cannot be selected while a character is holding the Tome, so be mindful.
Speaking of holding the tome, it’s a good idea to develop a designated Tome-Bearer for Free Dungeons. You really, really don’t want enemies hitting your Tome in Free Dungeons, trust me.
If one character picks up another and wields them as a weapon, the stats of the character being wielded are factored into damage. Thus, a very weak character (say, a freshly reincarnated Overlord/guest character) can still inflict massive damage by wielding a very powerful character (say, a beefy generic unit with 100 bonus points in atk, incarnated using a belt as the base item).
There is an upper limit on the amount of HL (money) that you can earn per floor/stage. I don’t remember what the number is, but every digit in it was 9. I used to farm HL by inviting a level 9,999 Food Market to stage 1-1 and throwing an enemy into it. This would cause the food market to start spawning a level 9,999 enemy every turn. I would use a unit with +80% money skill and the Shop facility bonus to kill 3-4 of them, and that would be enough to max out my HL acquisition for the stage. As far as I know, this is the fastest way to farm HL.
Speaking of HL, the fastest way (as far as I know) to farm MT (for repairing and renovating vehicles) is to spend HL on expensive items and then convert those items to MT. That’s how I farmed the insane amount of MT it took to renovate the Yoshitsuna and Super Robo Suit to 5,981 (you can’t renovate them beyond 5,981 because the MT cost counter is bugged).
Level 99 enemies are special and award about as much experience as level 300 enemies when defeated. This is somewhat of a tradition in NIS SRPG games and Makai Kingdom is not an exception.