I'd suggest to start with an all-temp wax. I've only recently gone to temp specific wax. The brand could be up to you. I wasn't sure which brand I wanted to use, that's why I'm trying them all out. I get a small block, use it, then move to a different brand. Eventually I'll find one I like the best. Besides most of the small blocks, regardless of brand, are in the $8 - $10 range
Any plexiglass will work. Metal scrapers are easier and will reduce the effort of scraping. I used my plexiglass scraper the first 5 or 6 wax jobs, til I got comfortable with waxing boards, then moved to the metal.
Flatbase riding will come along with more practice too. I wasn't able to do it very well until I really got a good feel for my board, and how to apply pressure in various ways for the things I was trying to do.