What level is he? If he's not 60 then go and play till he is! Plus, you may want to dedicate that wizard to one paticular thing, like crafting, or gardening, or pet training. A Storm wizard will be good for doing things like collecting pets or other drops, since he can easily defeat the enemy, meaning more defeats overall. A Life wizard might be good for crafting, since they can survive in a battle if they get caught in one while trying to collect reagents.
You shouldn't delete any wizard unless you really want to start a new and different school (especially if the wizard to be deleted is over level 10). Just because you don't play that wizard very often doesn't mean it can't have it's uses. You could transfer overflow items to it, create more garden space with it, or use it specifically for pet training (keeping full energy for your other wizards).
