Don't over-think it, all these options may seem important, but since this is just a bicycle to start out with and you have no opinions you can get whatever.

My advice, buy used.. $500 range, something with flat bar, upright seating, eyelets for racks and fenders. Save the cash for other stuff you'll need, spare parts, panniers or a different saddle. Then go buy a nice lock, the crappier your bicycle and the better the lock the longer you can let it stay parked in one spot while you do your stuff.