My recommendation for starting a new league is create something with a level of familiarity and something you can look at background for.
Create a historical league during the 1980s, then restructure the league to have 12 or less teams. Have a fantasy draft.
I say the 1980s because there is a good diversity with types of players (prior to the power explosion and disapearance of speed), you've possibly heard of them and lived during their playing time, and there is time for the league to advance, and you can do a quick internet search to find out about them.
www.baseball-reference.com/bullpen or
www.wikipedia.com
Under 12 teams so your league will be small enough to follow and learn about stars and what makes them stars.
Then have 1 level of minors. This way it's familiar to a Junior Club in
Football or Rugby.
Start off with basic rules for the minor leagues, use wikipedia to see what rules you want. Later you can expand it if you like.
As for learning about the game and it's history you can check out various movies and books...but that can be another thread.