If I were going to dump $15k into a focus, I'd be going for a full-out race car for the NASA spec Focus racing series. Or maybe I would buy a used fully-prepped rally car and just try out one of my dreams. It's your money in the end, but I wouldn't dump such a large amount into a car you've yet to even race. The only way to know what your car needs to better adapt to your driving style and your driving style to adjust for its driving character for maximum speed is to learn how to drive it the way it is.
Better yet, save all that money for track days and other events for the next decade for you and whatever car you have at the time. Build a used stripped race car for fun! The possibilities are endless.
If I could, I would buy a used sports bike, and make it into a track going vehicle. They're less expensive to maintain, run, and replace, blah, blah... this is a focus forum.
You just have to suck it up and try it. Spend that measely $25-50 to participate, stop making excuses to not do it, and just go and have the fun everyone keeps telling you that you'll have. Learn much more about how to drive your car in a legal and safe environment in good company. Honestly, you have nothing to lose but the time you waste telling yourself, "I'll do it once I..."
Enough preaching and to answer the original post, yes I do participate in SCCA events - specifically, Solo II. I run STS, and I'm in first place right now out of consistency of attendance.
I was doing very well starting out in the season and slowly closing the gap on the best competitor in my class. However, as of late I have been losing time on him. I think it's time for a driving school... and uh, to install that Koni Sport Kit that's been sitting in my garage for over a month and a half now. I'm actually considering selling it and possibly getting camber plates instead since those (I believe) would be more beneficial than a stiffer suspension. Ideally, I should keep the suspension and eventually get the camber plates, but money runs low. I still need to pay off the money I owe my university and enroll for the fall!