I think the most important thing is... start small. Make a small league (8 teams or so) and play through the games, watching what the computer does (which in your case will help, the computer does strange things but you'll grow into being angry at those like the rest of us!). Play with no minors or only a couple of levels; the real MLB setup is so many players I often delete whole minor leagues just to have fewer players to manage. Baseball broadcasts with smart commentators can be very helpful. The Mets' broadcasters are very good, sometimes very critical of players and managers, and generally fun. This season they've posted two full games on Youtube where they live-cast an MLB the Show game. They're very entertaining and would probably be helpful to you.
https://www.youtube.com/watch?v=C4ee_OdHEj0 https://www.youtube.com/watch?v=F7nsIOJ3Vg4 For a very basic guide, I think this is one of the best:
https://archive.org/details/High_Hea...Strategy_Guide It's from the last computer baseball game I played before switching to OOTP forever... it's very basic, but it's only 20 pages and I think will be helpful for you. Good luck!