Theres lots of information out there on the web. Here’s a list of resources that’s helped me along the way.
Scott ‘driver61’ Mansell has done a fantastic job of analysing and teaching us how to emulate the very best drivers. His ‘Driver’s University series is a great place to start learning the correct techniques to finding those extra few hundredths of a second.
Sam at McKee Motorsport for inspiration that you don’t need a sky high budget to go motor racing. He runs a very successful E36 328i with many podium finishes including class wins. He’s been extremely helpful in helping me avoid some nasty pitfalls, spring rate discussions (I’ve settled on 950 front and 450 rear as a result), staying ‘square’ on the wheel front so I can rotate tyres around during the season to reduce cost since the front left tyre always takes a beating. His website (here) also goes into detail about his car.
50sKid Channel for general maintenance with a lot of M54 specifics including an M54 engine rebuild, removing control arms and general servicing.
BuildaBeemer Channel for an South African e46 build including intake mods and engine rebuild with oil pump chain tensioner, diff swap, poly bushes etc. They’re obviously excellent motor engineers with great standard practices.