It's all in the guides
421 mani
Bigger tb
Engine work
866 or other cam
Really depends on your insurance, budget etc there's no point going excessive on a road car with cams and very light flywheels it'll just be poor to drive. Best bet is to sort wheels tyres, suspension first but check on the insurance. These aren't really like your corsas, Saxo etc where all performance parts are on the shelf it takes a bit of work with these. Just ask yourself if you want a quick car or a quick cento