Mine came with a few games on the internal memory too, so a card isn’t strictly needed if you just want to mess around with what’s there. I ended up throwing in an old 32GB card I had lying around from a phone though, mostly because I wanted to try some titles that weren’t included. Loading games onto it was fine, nothing complicated. If you already have a spare card sitting in a drawer somewhere, just use that. No reason to buy one before you even know what’s on the thing.
Mine’s also just a drawer kit and I’ve never regretted keeping it small. The one thing I did add was a copy of our vet’s number and the closest emergency clinic on a sticky note in the lid, since I blank on that stuff when I’m tired.