Keep your Squadleader as low level as possible so u can use your levels for free energy
Stock up on Powershots, Brain Bugs, and Mind Erasers for points, and Medkits to keep your team going
Clearly you will want the strongest/fastest mob killing team you can put together, but you don't need top tier pvp guys to clear towers
As far as amount of items needed I have no idea, but my guess is that anyone who has a low level warlord will be able to place pretty high from free levels alone. Then again trading just came out...so the competition will be trading their guys to fresh accounts woth low level warlords and trading for items as well