Everything needs to be CLEAN CLEAN CLEAN. You can have the best measuring tools in the world but if there is dust and dirt on your parts you are screwed. My old engine builder used Marvel Mystery Oil to clean parts. Even after a bore has been jet and ultrasonic cleaned you can wipe it down with Marvels and get ALOT of crap off the walls.
I agree dont buy cheap china tools you find on ebay. It also doesnt make sense to buy $$$ tools you may only use once. Maybe ask to borrow what you dont have.