here's a good strategy i found fully upgrade your towers i really didn't upgrade my self cuz i didn't get hit often and if i did die the towers would take care of them selves, also i found the triple threats to be really good fully upgraded.
oh well with the ours of skill i got i guess i'll just have to do it again and make sure my space is at unlimited so it will save this time reading all the description would have saved me a lot of time