What kind of spell do you like?

May blessings prevail: for example, cast Vampire Touch and Dragon Strength on some creature of level 4!

Yes, but there is a tricky spell called "Steal Charm".:D

...rather than Weakness or Curse on creatures of levels 1-3.

Why necessarily Weakness or Curse? And why on levels 1-3?.
Curse can also be Blindness, Hypnosis, Plague, which clearly won't hinder the game.:)