Best advice is to not take advice (till verified). Everything you have already been told, before you act on it, research it. Even your growing friend gave confusing advice. As said, the ads you see are reputable breeders and have been doing so for some time. You would be hard pressed to see people buying unknown strain/phenotypes from unknown breeders, let alone a non grower. I would never pay for a bag seed even if I knew the strain.
Research soil, lighting, dwc, airo, hydro, and whatever growing aspects you want to try (although soil may be best for a newbie). Growing for the first time is a definate thrill. Make sure to plant a few beans to hope for a female out of (let's say)3 sprouts.
There are a great bunch of folks here that can and will help you along the way, just be sure to research whatever advice you do get. Going with your gut alot works for me.