Welcome to TE! Best advice I can give about shifting is to "mess around" with shifting the gears a little. It the best way I've found to get a feel of how they work. Eventually it will become second nature. One piece of advice I heard from a local rider to a newbie on hills was "Shift early, shift often."

As far as finding inexpensive shorts, try just typing in womens bicycle shorts/jersey into your browser search engine. You'd be surprised at what shows up. I do recommend trying some one at your LBS to get an idea of proper sizing. Also try EBay.