This is for the 4 instruments, Band challenges are not needed.
The challenge rewards are Gold, Platinum, Diamond, so Gold is actually pretty easy to get, alot of them can be obtained on easy.
The only one I had issue with was vocals, because I am terrible at them, so I used the Taylor Swift song 'Love Story' as all that is required for gold, is to obtain star power.
So you don't need to be able to chain, or get good scores, you just need to be able to hit 3-4 phases