Ask for references. (Insist, actually.) I suggest you ask in the thread, which is standard etiquette for newbies (certainly includes anyone selling on board for first time).
Many newbs have sold a while on ebay- a long history there has generally been good enough for me.
Others have sold to board members, and will give the references in thread.
Would stay far away from a 13 reply newb who never sold on board, even if they report 'many sales on instagram' or something- which imo is useless without someone you know and trust vouching for the newb.