Generally, Gigabyte (and Asus) have always produced reliable and well regarded mobos, so I would recommend sticking to one of these brands for the most part.
As for which processor to buy, I'm an AMD man myself just because they're cheaper than Intel for the equivalent processing power. Buy the best CPU that you can afford; if you plot a graph of clock speed against price for a give CPU range (e.g. Phenom X2) it should be a roughly straight line upto the point where you start paying a premium for the latest technology. This is often a good place to start.