It will take time to build relationships in this community, but well worth it. Give it some time
Scammers and unethical buyers are all over, and leave a bad impression. Being a new member, a few sellers will be wary of this when seeing your profile.
Everyone above has mentioned cash on the glass, that will be your best bet.
PM to a seller is a good start, but be patient as most of us on this forum have different check in times.
Overall, welcome to the community, and good luck in your hunt for awesome games!