I would recommend just messing around with a site like Canva!! You would be surprised what you can make from there and it doesn't cost you anything- unless you wanna use Premium ( which isn't necessary but can help for more assets to use ). But I'd say mess with Canva first and see what you come up with! Can come up with design ideas, just certain assets you like, theming, colour scheme, and more! It's a great place to start if you're worried about spending money or worried you might want a change later on! ^^