The regular iPad is totally fine for what you're doing. i use an older one for sketching my garden designs and it handles Procreate without any drama, no fancy iPad Pro needed. the Air is nice and all but you're paying extra for stuff you won't actually use if you're just doing character sketches. the base model's got a good enough processor, the screen's decent, and it takes the Apple Pencil just fine. save yourself the cash.
the main thing is making sure you get enough storage - go for at least 256GB if you can swing it because Procreate files and all those brushes add up quick, trust me on that. also check if the current base iPad supports the newer Apple Pencil or if you need an older one, prices vary. honestly for fan art and character work you don't need pressure sensitivity levels that would make a pro photographer weep. the regular iPad will do the job and your wallet won't hate you. i'd rather spend the money you save on actual good brushes and maybe upgrading your Apple Pencil over time if you need to.