It's been a little over a year since I stepped out from behind the engine, but I think I'd like a go at it.
Toby: seat time and skills are everything. As previously suggested, set the car up, and then spend some serious time learning. Only after you can't get the car any faster should you spend more money. (I did it backwards, and spend too much $$ from the outset. It was only after two+ years of continuous training and religious attendance at every event with constant tips from the best drivers that I could take a lap without complete embarrassment. Don't spend your money, spend your time. Work on the fundamentals ... especially looking ahead and good braking skills ... and remember that you can never be too smooth.)
I try to beat myself each event; reduce my differential to TTOD. I'm 52, will never again have 19 year old reflexes, will never be an F1 driver. But I do have 20+ years of a fun hobby, and surely I can get a bit better each year.
So I'm in the camp of more instruction until you can recognize and define the problem your car has that you can't fix by driving better.
Probably the smartest thing I've heard on the forum in months. Sage insight, Curt.
Keep me in the loop, Tim.