Myflies is a good choice in that at least one of the tiers is a regular and productive contributor to the site as well as an award winning tier. I'm sure a quick note to Mr. Myers will get you some specific counsel on recommended flies. see here: http://www.paflyfish.com/modules/smartsection/item.php?itemid=197
I know that many people like http://www.theflystop.com/index.cfm as many of us have met the owner when he worked at the outdoor shop in volant. they are cheap, too.
as far as a very basic fly selection for PA, you don't need to go crazy to start. some hare's ears for nymphs in #14 & 16, wooly buggers for streamers in black and a light color, caddis pupa #14, and for dries go with adams 14-18, sulphers in 14-18, and a caddis dry of your choice.
It will be extremely easy to build upon that, but for starters...those are some must haves!
Beyond that, I would start looking at terrestrials (ants, hoppers, beetles, bees), stonefly (both nymph and dry), basic midge (pupa and dry), and junk flies (san juan, green weenies, egg flies).
The next stage, you can start getting into specific imitations for specific mayflies and stages (bwos, green drakes, hendricksons, etc in different variations such as emergers, cripples, comparaduns, parachutes).