Essential Tools and Parts
I use the following products exclusively on my own car, and you can too. Clickable links are Amazon affiliate links that help keep gas in my tank when you purchase through them.
For general parts cleaning and a thousand other things, I use GumOut Carb and Choke Cleaner. For lubricating most parts that slide, or any small part that rotates, I use Super Lube. It's safe for plastic, good in freezing temperatures, and clear, so your clothes don't look like a superfund site. Every first-time Air-Schooled student must have those two items, and a roll of paper towels.
For harder-working metal parts like wheel bearings and CV joints, Valvoline Durablend Semi-Synthetic grease works great. For a few bucks more, I prefer the slightly more pungent smell of the Valvoline Synpower Synthetic grease, though I can not actually tell any differences in performance under 75mph/120kph.
One of my favorite tools, the best voltmeter I've ever used is back for sale on Amazon after a brief hiatus. It's a "pen type" meter, meaning you can always see the screen and the cords won't melt on the muffler while you troubleshoot a broken electronic ignition module.
I strongly encourage owners of fuel-injected Volkswagens to have a Bosch 2 Noid light for their car. This will save hours of time and frustration when diagnosing issues.