The key is that area-of-effect spells (fireball, meteor shower) don't work on the magic mirror. That is, against Jalib, you should cast area-of-effect spells, completely neutralizing the advantages of his specialization.

Gremlyns - first, for faster leveling, use master gremlyns (they resurrect golems). Then - gremlyns-troublemakers (attack 5, that's great!)
Gargoyles - it doesn't matter, they always play the role of tough meat for me.
Golems - both upgrades are good; the new ones allow you to use the following tactic:
Leave only golems, cast a wall of fire, and run them back and forth through the fire, showering them with fireballs.
Mages - when their number exceeds 50, I think it's worth taking new combat mages.
Djinns - it doesn't matter, as they don't live long.
Rakshasas - the new ones, as with their attack on multiple targets, mini-arts for luck, attack, and speed, they can decide the outcome of the battle in one hit.
Titans - both are almost the same; I prefer the new ones because of the summoning of a storm.