I would not build a track car just yet. Most important tool is you as the driver. I suggest going to as many track dates as possible next summer, and try diff tracks. BMWCC events are great, go to at least 2 of those if you can. Over at www.e46toronto.ca
we organize a few track events aswell. Make sure you instruction, thats very important. After you got some good track miles, then build the car. Also, dont start modying your car like crazy for track, learn to drive first, then spend the $$ on mods and track cars. Good luck.