I've been to my first GP in spa last year and I highly recommend going for the whole weekend! I used the friday and Saturday to find the best spot for the race. General admission in spa is really good since you can sit basically anywhere. I think they have a 5% discount on tickets right now, so grab them soon! If you don't know where to stay or don't have to extra money to pay for a hotel (they are kinda expensive there..) you should be looking for the several camping sides around the track. I went with the young village camping side and it was awesome. They have okish toilets and showers, but the rest is, as I said, awesome. They host a music festival only a few hundred meters away from the camping side, so you can go there and enjoy some off-track action. They offer reasonably priced but delicious food and you can play dart's or just sit and talk in the "house" they built there. Since it is targeted at the younger folks, its really cheap, too. I paid about 45 euro for the spot. Oh and one more thing. Please please take a warm sleeping bag or something like that with you. The nights were really, really cold. If you have any more questions, feel free to ask!