E30 Go Kart project.....How would you begin???

[Mr. Tasty]

Buy a Cooper S.

ftfy

[GillesBigCowboy]

Simple, make it a racecar and join the fun.

[Wild Ride]

Camber
Sticky low treadwear extreme performance summer tires 225 like hankook rs3/bfg rival
15" Ultralight wheels like enkei @ 9 lbs
Ast 4100 coil overs (elephant Motorsports has a special on these)
Z3 rack
all new/Solid bushings
Short shifter
LSD
Front strut brace like Ireland engineering
Front lower x brace (race skids)
Skid plate
Swaybars (start with front only)
Smaller steering wheel
M3 offset control arm bushings
aggressive street performance street brake pads on stock rotors
New OEM brake lines or at the very least new fluid, it will improve feel dramatically

Lots of autocross