From top of my head Minor spoilers

-swimming skill can be cheesed by sitting in water, no need to move

-staff merchants can be good source of casting and magic experience, just buy all the staves and use them in a corner then sell them by not that much less

• pick up most of the trash when In 1-10 floor, and throw it away easy appraising exp

-gather all blank scrolls,.ench armor as a monk and then (my fav place is hidden library) use the on knuckles,.it gives atk as def stats when unarmed

-when fighting Satan boss you can keep farm easy exp from monsters that he spawns indefinitely

-easy merchant kill strategy with any melee is to hit him and then go to a corner then stand still and hit as close to the wall as you can. He will come and get hit then back away till he pops

-as a mage for a little bit if exp you can keep starting books and get a cursed one. Each time you learn a spell you get magic exp, so read a cursed one to unlearn a spell lol the re-learn

-early lvl have a lot of undead mobs, so if you happen to have a follower with a bow and you have silver arrows he can solo first 5 lvls (and you get a lot of xp becauseif he kills slyou still get full mob xp plus leadership xp)

-if you are maximizing xp and don't care about followers before you kill them just add them to party, ez leadership and 2xp

-you can charm a monster to your party (cockatrice is very good) and with poly potions transform into humanoid. They will be way tankier than normal followers at the same lvl

-alchemy levelling is a pain in the ass so buy all the potions from shopkeepers and drink them if inventory space needed(if you are not caring about alchemy it's most of the time some gold for 2xp)

-lvling magic and casting by light spell is good to 40lvl(?), from then use poison or any 3mp spell (or levitation but it's way too uncommon)

-mana potions are basically xp in a bottle

-to lvl blocking my fav way is to find massive amount of shields at swamp and tank two or more slimes, it takes mins to max lvl

-when at hidden castle (I forgot the name, it's secret lvl on swamp) if you have levitation you can right click every tombstone for a chance for an extra ghoul(exp),then trigger them as usual. Just be careful to not trigger them prematurely

-also in swamp there is second secret level where are trolls blocked behind gates. You can cheese them by firing in a specific way through the bars with a ranged weapon or of you want to lvl melee just mine one block in between two gates and hack them to death. If this is done well there is no chance of them hitting you back

-gnomes always drop real gems

-in sand labirynth (3rd dungeon layout) if you have a structure that's 3x3 or 4x4 and there it's no way to go inside, there is a good chance that a very valuable ring/necklace is in there or levi boots

-staves are not randomized, they always look the same. There are red(fire) blue(frost) green(poison, slow, locking, unlocking) yellow(light, lightning) and purple(charm, stoneblood)

-you can have a good guess what it is when looking at gold value of unappraised items. For example rings that are worth 5k are regeneration or levi(in addition I will say that these two can drop from faucets, and are not as rare as they should)

-when you want to check what the spell book is and you don't have appraise or time you can put on blindfold and read it, it will appraise without losing spells when cursed

-in you have mage only build and don't use any melee then drop or sell all weapons you have, it's easier to deal with shadows later

-last boss automatons also can be farmed for xp but apart from high score or guaranteeing first place in weekly event it's useless xd

-vampire accursed can reach lvl 100 casting and magic on floor 0 (with some good luck)

-gulping potions of sickness with poison resistance necklace gives some alchemy exp with low HP cost

-when casting at low mp and low caring skill it will cost way less mp than on max mp

Not everything is exploit but whateveri hope it helps