When I saw the title I thought it was someone wanting help with losing weight!!
That question is way too vague to answer properly - there's lots of different limitations on partition sizes depending on what OS you're running, and even then you get into situations where you can read bigger partitions than you can create - it's all a bit messed up to be honest.
The main limitation people find with FAT32 is that you can't have files bigger than 4GB. No issue back when hard drives were 1/4 that size, but these days people frequently run into that limit.