Ratchet & Clank: Up Your Arsenal Tips

Easy experience!
When you start a new game and go through it, only buy a few weapons, no more than 12. When you start a challenge mode, you will have lots of money.
Buy a few normal weapons (NOT Mega Weapons!) and kill all the enemies. all original weapons will upgrade very fast, and some will upgrade after just 2 or 3 enemies, even small ones!