To power level an alternate character, simply put a high level gem on them to have them reach stats that normally are not available to low level characters. At Level 20, socket armor and weapons become plentiful. You can put on Level 60 gems to have a very powerful force, even without a high level character. If you later need to remove a gem and place it on superior gear, you can have the blacksmith break the armor or you can remove it with gold using the gem remover.