here's a tip:start with Iron tower(don't cost Any points to other tower) then upgrade it,when it's fully upgrade it's damage is 7 right? buy another tower not any, only iron cause it's damage is 7 so when it's also fully upgrade buy 3 Iron towers then max the upgrade then now You can buy other towers.
I have a question: Is the Wave not Manually? A:NO,it's manually I've saw the next wave so I clicked it but i accidentally pressed it!!!! so i hate manual next wave. "+" if you also find it out and please don't "hyphen" it