E90 M3 was my first 'track' car, it's fantastic for it. Neutral, balanced, predictable with a good amount of grunt. It's heavy but even a mild coil over setup will make it feel way more responsive in transitions. I tracked on just pads/fluid, but if your serious I would just go straight to a BBK. You can also cruise to and from the track in comfort and relative quiet. When you've just done 3 days at full adrenaline pounding around the track and are totally knackered, the refinement is very welcome. The BRZ/Miata are cheap to track for sure, but honestly when your getting ripped on the straight then held up through the corners by some boomer driving 5/10ths in his z06 you will very quickly wish you had more power
