I'm not too familiar with Maplestory mechanics, but Is upgrading stuff only possible through cash shop items?
Most everything related to weapons is obtainable at a slower rate and even the difference between a free players gear at a decent gear level vs a maxed out player isn't quite that enormous.
I have heard horror stories about how abyssmal Brooch sets and their additional effects are, but it's hardly a make or break you upgrade that's required.