avoid 3 block clears, they're not worth enough points. figure out shapes that will clear 5+ blocks. Learn tricks to set up combos, set up a volatile shape like a zig zag and put in a "key" of another color you can detonate to allow it to clear. If you can start pulling that off, you can learn to put a key in to detonate the key, and so on. But consistency with big clears and modest combos should get you further than betting on random long combos.
Also, make your own color palette, it always helps people for some reason. Play a bunch and then let your brain dream on it, the subconscious aspect has to sink in overnight.

