The beauty of the game is in it's forced purist gameplay, that there's no "trying again". You fail, that's it.
Well, kinda. Finish a game, then go back and "continue" ='.'=
Now as far as the "what item affects whose damage", that one can be tricky, and the best thing for that is to swap the item out while looking next to their portrait at their damage. Ive wasted items on mages before that have no effect on their spells. Throwing daggers are a waste, period. The best thing, bar none, in my opinion is to give your meteor-flinging mage(s) fire resistance draining items. Every hit they make, all creatures take damage on their fire resistance. 3 hits later, if anyone is still left standing, their fire resistance is like -35 and you got more coming. Have two mages going, it's over!
But yeah, ghosts and basilisks are two of the more dreaded creatures to face. If you get "paralyze" type items, give them to a rogue or even better a non-meteored mage (paralyze wont work with meteor) el pronto, and get the creature frozen. A "rush" can help too, never underestimate the power of a well-timed rush.
I still get hammered to this day playing the game, sometimes youre just flat out overpowered and there's not much you can do but strategically start retreating members and hoping who's left can clean up!
Strangely enough, it seems that game length increases the difficulty steeper than actual difficulty settings do. Play a short game on challenge, then play a long game. Im not talking in the long run it will be more difficult, the first stages of a "long" game will be more difficult than the first stages of a "short" game.