What size USB should I get?

Hi! I’m realllyy not tech-savvy but have been given a 2014/15 MacBook Pro that I want to patch.

Could someone please explain in really simple terms what size USB I need to buy? OpenCore said the patch I need would be something like 28GB (from memory). Does this mean I just need to buy a 30GB USB drive or will it perform better with a bigger drive?

Sorry if this is a stupid question I just don’t want to spend money on something that would be useless lool - thank you!