As long as you stay away from Norinco and NEA you really can't go wrong. I've run NEA parts in a few of my builds with no problems but there have been way too many people with issues for me to be able to recommend one as someones first AR.
Buy what your budget allows and remember to save some money for an optic and 1000 rounds of ammo. These things are hungry (especially your first few trips to the range).
Some people will try to tell you that with the more expensive rifles you're paying for the brand name and nothing else, this is not true at all. The high end brand rifles that cost more typically use better coatings, have nicer fit and finish, come with better components (barrel, trigger, BCG), have better quality control, come with nicer furniture and have established themselves as a company that builds quality firearms and stands behind them with better customer service. If you only shoot a couple hundred rounds a year these things may not matter to you but if you run thousands of rounds a year in competition and practice days and want your rifle to continue to run then spending a little more up front may be worth it.
I would not go with a piston rifle for your first AR. There really is no advantage over a direct impingement rifle for a civilian shooter but the disadvantages are things like proprietary parts that you have to order and wait weeks for, increased weight, being stuck with the barrel it came with instead of being able to swap out to longer or shorter whenever you feel like it, increased cost.
If you do go with a piston rifle then I suggest a PWS, I've owned 2 of them and still have one, my rifle has over 5000 rounds through it and has never had a malfunction that wasn't my fault (not seating the mag properly). It still looks like new on the inside and is still capable of shooting 1 moa with match ammo.