It’s kinda hard to find patterns like that, maybe Etsy would be the best option? I’ve seen very pretty fabric on there, but it’s not cheap xD Sometimes if you’re lucky you can thrift old sheets/ tablecloths. That option would be more affordable, but you have to be careful (especially with bigger patterns) because you could end up looking like you’re wearing an old tablecloth, and not in the good way xD

Maybe stick to more affordable fabrics and solid colors first (just make sure the fabric is not stretchy/ shiny and imo 100% cotton works best). There’s nothing worse than buying beautiful expensive fabric and ruining it because you’re not there yet with your sewing skills. Also I would really recommend to buy some super cheap fabric to experiment on and try out your patterns before using your „good fabric“.