The strongest AI will choose the best possible moves, i.e. summon the most destructive monster it can, use the best spell it can, and move to the most advantageous position.
So consider these three aspects and try to figure out which choices are the best and how you can detect (from the game environment) why they are the best .
Movement is probably the hardest, you may need to have a short-term "goal" and over several turns the bot will walk toward goal (unless a new goal suddenly seems better). So at each turn, see what the best goal would be, and if it's better than the current goal then it replaces the current goal.
When you are playing, watch yourself and in different circumstances ask yourself why you are choosing a certain move or spell.
Hope that helps
