I'm new to pu too!
Essence of tea
both seem very reliable and do paypal
For very young pu I hear yunnan sourcing is a good spot also.
Gingko from Life in Teacup also has some nice samplers and an appealing butterfly toucha to consider.
I've tried a few 5ish year old pu but majority of my drinking has been 90's semi aged sheng (uncooked).
Many here will suggest you try a young, a semi aged, and an older one. Then also try a cooked. Houde has a decent looking aged shu (cooked) that I will try (if I ever feel the impulse for cooked). http://www.houdeasianart.com/index.php? ... 4024375163
Sadly most of the stuff I enjoyed from them has been sold out, so it's hard for me to recommend the other stuff that I have not yet tried.
I recently ordered a small number of samples from essence of tea (my first order from them), so if you would like me to keep you posted I can when they arrive.