There’s so much info out there, but my main thing for reborns, especially considering your age, is that these dolls aren’t toys. I know there are videos on Youtube with people feeding, bathing, even changing diapers with fake poo with their reborns, but that’s not how it really is. The videos are edited to make it look real, and even then those reborns are often handled wayyy too roughly.
Don’t change your reborn’s clothes too often, that could rub off paint over time. Be careful with the hair. Be as gentle as you would with a real baby, no rough pulling or holding by the head, limbs etc. Dark clothes should be put through the wash before putting on your reborn or the dye could rub off on the vinyl. Reborns are really collector items, not toys. They’re good for an occasional change, brush, cuddle, etc. But really more for display, I think.
As for buying, just make sure there are lots of clear pictures, with closeups and triple check the seller’s feedback to make sure you won’t get scammed. Good luck!