I intend to buy a AMD Radeon r9 280x for mining vanilla coin.
I look for a tutorial that explains how to mining vanilla and how optimized the AMD Radeon r9 280x for 400 Mh / s
Just download Smolen's miner and run it. I wouldn't advise to buy a GPU just now for mining Vanillacoins (or anything else) though, since block rewards dropped to 88 and FPGA's are just around the corner which will be far better in terms of energy efficiency.
But if you plan on buying a good GPU anyway for gaming and etc., go on.