I’m a 13 yr old girl so maybe I can help! Like others have said, try to inquire about what she likes. Some things I would like to receive and girls my age generally like are skincare (e.l.f is a good, cheap brand), makeup, jibbitiz (those croc charms), Sanrio merch, books and bookmarks, succulents in cute planters, hand sanitizer atomizers (I don’t really get the point but they seem popular?), perfume, duffle bags, plushies, fuzzy socks, lamps that project things, night lights, lip balms, mini backpacks, coloring books, logic puzzles, fairy lights, room decor like posters or wall hangings, etc. If you can afford it, you could make her gift an “experience” like taking her to a movie or a performance but you should probably check in with her parents to see if they are okay with that. On the more expensive end you could buy her a piece of clothing that she has mentioned she wants. I’ve also seen people make their SO “coupons” which I think is a cute idea. Also, if you are crafty and can make a gift I’m sure she would love that a lot, even if it only cost a few dollars because she can tell you put effort into making it. I’ve never dated, but those are some things I could imagine giving to my friends. Hope this at least somewhat helped