Okay... this may sound different from everything else you've heard and not very frugal, but... buy what you want. I've been wearing glasses since I was 8 and now, at not-even-30, without glasses I cannot see what's in front of me until it's 5 inches from my face -- no exagerating! Re: the lens tips everyone has given, I agree completely. Do the anti-scratch, polycarbonate, etc. In regards to the frames, here's my advice. Since you are starting out and you don't know yet how frequently you'll need to replace your lenses/frames, you don't want to spend too much. Search around, price compare, etc. However, if you discover that you only need to update everything every few years invest wisely.
I only replace my glasses (frames and lenses) every 4 or 5 years b/c it takes that long for my eyes to change and need a new prescription. My insurance only gives me maybe a 10% discount, so not really all that helpful.... The coupons are usually pretty good deals, but there are better if you shop around. I bought what I have now a year ago from LensCrafters. I searched 3 stores for a style that fit my face well and I didn't even look at the price. I wanted something that fit me well and looked good, too. I mean, they're on my face which is what people are looking at every day (unfortunate, but true). I spent $350 on what I have now; they are hybrid frames with metal surrounding the lenses and plastic ear pieces.
I take them to back to the shop where I bought them to have them adjusted and have the nose pieces changed every 6 months at no additional cost to me. They also check the screws and give them a general once over to make sure everything is holding up well. Anything that needs adjusting is repaired; again, this is at no additional cost. Make sure you buy them from a place that will do the same thing for you. Glasses need to sit properly on your face so your eyes are looking out through the correct area of the lenses, so even if you tighten the screws yourself when they loosen, you'll still need to have them professionally adjusted and nose pieces changed every 6 months. Otherwise you just spend all day pushing them up your nose.
Good luck!