He's right, you have too many pillars. What you really need is more towers. Try to replace around 5-6 pillars with towers to make it more balanced. Until you get enough money to upgrade those cards, you're going to have to farm a low level AI. I think AI -27 would be good. If you're having trouble you can go with AI -28. It should only take about six straight weeks of farming to upgrade. After that your deck should be good to go. Have fun!