just fyi, once you hit level 50, every time you level up you get a jewel.
also, you can only play through survival once - after that you start again from the highest level you did
lol so i played the arcade mode at around level 6 - got to level 8. farmed up about 1k rage and just kept rolling side to side killing everyone. unlocked cheats: looney, bin, rackem, adiosturdnuggets, prime, trashly
I had so much trouble getting through the first few stages until I realised I could have more than one ship. I couldn't get through the other towns until I realised you could upgrade the ships. I just couldn't get through the boss until I realised there were upgrades you could get from stars... maybe all this information should be a bit more obvious?