Try to use as many as possible by borrowing other pilots' sets for a flight. Headsets are very individual, and are something you should really try out, not just take the advice of other pilots.
Many have had had good results with the Bose (expensive with no passive noise regulation, but lightweight and effective with the active noise truned on too), David Clark (they're the most popular one out there, so there must be something more to them than their trademark green color), Flight Com Denali (great if it fits, but seems to fit smaller male heads and females only), and Lightspeed (great comfort and good noise CX, but a bit heavy an cumbersome in smaller cockpits).
There are too many variables to suggest any one. Do you plan on going pro or just getting the ratings. Maybe spending the extra $ is worth it if you're gonna' keep the headset for awhile. XC flights often are trying on cheap headsets, though tey work great for local flights of less than 2 hours.
Try to find 3-4 you find comfortable initially, and then wear each one for at least 2 hours while studying (if you can't wear them while flying, which is ideal). Often times, as long as you stay in the FBO, most FBO's won't object to you wearing the headset provided you appear to be clean and well groomed.
I personally find light weight, gel ear seals and noise CX to be my most important areas of my headset, but, Those are my pet peeves, not yours.
Sennheiser makes a good product, but TRY before you BUY!
-Boo!