JJ Blood Mage: A gnome blood mage with mage plate and JJ (the only reliable god for mages right now) could get up to 36 MP at level 8 and and still have 6 potions remaining. It would be able to get 42 casts, and the loss of HP with each MP potion can be covered by HP potions and their ability to drink blood pools. 42 fireball casts would deal 1344 damage at lvl 8 and 1680 damage at lvl 10.
An elf blood mage could get 42 MP at level 10 with this strategy and have 1 remaining potion, then buy a keg of mana and get 4 potions. It would be possible to get 35 casts and chaos avatar, wich is useful for fighting enemies with high defense. 35 casts at lvl 10 would deal 1400 damage.
Blood mages are hard to level up with, because of their lack of resources to fight high level monsters. This is the advantage of using an elf .
JJ Warlord: You can get 10 potions as a gnome warlord, bring a sensation stone and a conversion seal and buy a keg of mana, so you will have around 17 potions. If you transform 3 of them into MP with JJ, you can get 25 MP, enough to get 10 MP per potion.
With your 14 potions, plus 2 protections from your initial 25 MP, plus 1 protection you can get before you start fighting, it's possible to get 17 protections. Assuming you have 40 base damage and 90% bonus from the warlord's abilities (76 damage), it's possible to deal 1292 damage to a boss without physical resist, if you didn't buy the berserker blade and didn't drink health potions.
JJ Thief: Use a halfling thief with the tri-sword. Worship JJ and get his "Boost mana" boon 3 times. Enjoy the extra power!
Note: Works well with most glyphs, specially HALPMEH.
Note2: Use "boost health" 1 or 2 times if you'd rather have +15 HP than +3 base damage.