you should put in stuff like quartz and gold and make stuff like rings and then put in diamonds and get money from it then make a shop that sells armour then be able to put armor on pesants that you can hire for a day. and if you could buy diamonds for other things like gold persay then buy rings he made with the gold!
the strategy i use is this: go 2 waves at a time then combine gems and switch and make a new one then combine those and put them in the towers then sit back and watch them all DIE!!!!!
Not a bad idea :)