I would suggest getting cards from different issues - e.g. don't go all in on any one issue. There are hundreds of pre-war issues and you can get a hall of famer in most of them for under $100. Feel free to look around at OldCardboard or VintageCardPrices for a list of most issues with photos. You can peruse my album
here as well, which shows my favorite card from 50 or so different pre-war issues.
Find what you like and start there - your taste will evolve as you learn more.