I am a newbie for years too

If u choose a MLB team u dont have to manage the MLB team, u have to mange the minors too. Yes, the AI can do that for u, but its another level of complexity.
After that, u have to mange the drafts. Roster movement is the next problem (waiver, ...). Ah, yes dont forget the rule 5. Lets talk about contracts and arbitration. After that, the stats and how to evaluate a player.
I think the game is overwehlming at the MLB level for a new player.
My suggestion for u, dont eat the whole pie at once. Start in europe (yes, we play baseball too

), a league like "Baseball Bundesliga (Germany)", or "Honkbal Hoofdklasse" (netherlands).
Why???????
Because these teams dont have minors (no complex roster moves), they have easy contracts and u dont know the players.
With this teams u have to learn fewer things:
- How to set a team for a game
- Choose Players from a simple player pool
- Learn how to evaluate players (starter, bench or secondary roster).
- Handle injuries
- Free Agent trades with a small amount of money
After some sessions, u can choose a league with a small minor system like Nippon or Korean league. At this point u start knowing WHY u need a minor team and which player should play at your minors.
This type of games (start in europe, start in asia) can easy set up with ottp. At the start screen choose "New standard game", in the next screen u can choose which leages u wanne play. Thats it.
I hope u realy enjoy this great game.