In case we have lurkers in this forum, a good tip for people to progress without spending is focus on the uncommon speed "first strike" tanks. Try working on Cpt Blitz and Lightening. Use a team of 3 speed tanks and 1 assault tank. Start with respin 1, respin all, mini strike/ion strike, and of course target. Your goal is to fight the Computer controlled tanks and first trike there rare/super rare tanks and kill them on the first turn. Your only main weakness is Jammer since it can screw up your target but if you can kill one tank and get one material. It is worth it in the long run. Happy farming guys! If requested I will throw out a spew on tank special abilities such as multi strike/others and abilities used by ability points.