sniper and scatter, right at the beginning. and just spam the upgrades.
I have the ball speed maxed out (except for speed limit to 60), hella ball power, and the cash bonus maxed out.
The cash bonus helps to spam the fk out of the speed upgrade while spamming more balls. And make sure you have the 10 ball upgrade for the scatter ball. Really helps.
Haven't been able to get faster than 30s.