cannot figure out why i cannot purchase anything from the mage guild--- ever... i keep trying and only get the "check mark" when i try to buy a spell

You don't *buy* spells. If a hero with a spellbook visits a town with a mage guild (and prerequisites depending on the game are met, you didn't say WHICH OF THE FIVE GAMES you meant), spells are learned automatically.

The one thing you should be able to buy is the spell book itself (I seem to remember), for a hero who doesn't already have one. Which means at least some of the "mighty" heroes in at least some of the games.

First question is "which game were you talking about?". After that, details can be offered.