While not necessarily for ///M cars, keep track of what goes on at Infineon Raceway, as it is a stone's throw away from SF. There are plenty of schools there and various events, I myself did a 2-day RS 4/R8 Performance Driving School back in 2008. Incidentally, there was a BMW Alpina event the second day and we drove alongside Z8 Alpinas (and B7s) and Alpina's owner (Andy Bovensiepen - the son of Burkard, founder of Alpina) very own track prepped E30 M3, which slaughtered even GT3 Porsches believe it or not (Andy is a pro). Still have pics somewhere of that beast.
There is also a race school there that works year round, and you can start off on lower classes of cars before moving to open wheel (I believe they have Miatas, so that's a good way to start exploring RWD capabilities on a much less powerful, albeit lighter car).
Kuddos to you for wanting to spend your first "mod" dollars on improving yourself!
2011 BMW E82 1///M: AW, ZPP+ZCV, HK, Apps; Akra CF+Valve control, MadDad mids, K&N, Forge FMIC, P3gauge, EuroTails, Tint, CF Mirrors+Spoiler+Roof+RevoZ diffuser, 10mm H&R, IND grills+gills, xCDV, LUX AE
2008 Audi B7 RS 4: Sprint Blue, Audi Exclusive Euro Interior, Premium+Titanium Package, EPL Tune, Stasis Ohlins MS coilovers, Milltek valved exhaust+DownPipes, Alcon BBK, Tint, ADR V1, Lidatek, Lamin-X, Strasse Forged SM7 3-piece concave wheels, 275/30/19 PSSs, Euro flat-bottom steering wheel, JHM SSK