Hi Albert, we are off to Hungaroring next weekend (not for the first time, either). Generally, it's better to buy your tickets online before the race, but you can purchase them at the gate as well. General admission at Hungary is pretty good (and only costs 90 EUR) - because the circuit is located in a natural valley, you can get good views of multiple corners, even from General Admission. The best place is up on the hill overlooking the final corner and pit straight.
The cheapest Bronze grandstands are only a little more expensive than General Admission and worth it, even if it is just for a seat for the race. If your budget can stretch, the Silver grandstands around the last corner are also great value for money at around 250 EUR for the weekend.
We did a ten-part travel guide for the Hungarian Grand Prix which you can read here: http://f1destination...and-prix-guide/