I'd suggest replacing the newer gem collection system (20 green, 10 blue, 1 ring) with the older purple gem one. Enemies and crates sometimes drop red, green or blue gems when shot, which messes up the gem count, but purple gems are an exception. The old system was fine, so I don't see a reason for having different types of gems. You could simply replace each green gem with one purple gem, each blue one with two and the gem ring with three, or something like that.