Do you know of any seed or plant exchange groups in the area?
Many plant societies have seed exchanges and plant sales and swaps. Since you don't mention any favorite plants, I refer you to a page on our Philadelphia Gardening Guide which lists local plant societies
You will want to visit their web sites to get details on their seed exchanges. Two plant societies with notable seed exchanges are the Hardy Plant Society Mid-Atlantic Group and the Delaware Valley Chapter of the North American Rock Garden Society.
The Philadelphia Gardening Guide is a great starting place to learn where to buy plants, what to grow, how to connect with other gardeners and where to learn more for gardening in this region. And of course, becoming a PHS member will put you into contact with great gardeners and lots of opportunities to learn more about gardening.