Brake fluid change is a must, and tbh for £50 I'd chuck a set of Goodridge brake lines on there too.
If you don't have one already then a front strut brace would be a great buy (the cheapy £105 one on eBay is more than good enough, it's a better shape than most too as it clears the brake fluid bottle), but other than that I'd say that a standard mk3 is good to go. Stock brakes will be fine with stock power, there's a load of chassis bracing I'd do too but you can get to that down the line, along with a decent seat and steering wheel.