Training; I have no idea how this works, can someone please explain how you should train your squad?
There are some fairly extensive guides on the Help forums for stuff like this. I'd start there but the main thing would be deciding what you want to train. Either guards or big men (you can do SFs but save that for later)
Draft; I think I have a good handle on draft and scouting, how do I know what # I am likely to be picking at in the draft? (Which I think is the 25th?)
The lower you are on the ladder, the higher your draft pick. For inter-conference rankings i think it goes by games won and then percentage points.
Scrimmages; is there only one scrimmage allowable per week? Should I be rotating players through the scrimmages to balance court time amongst my squad? (Once it is complete)
Yep, only 1 scrimmage per week. It's really just used to balance out your minutes after the 2 league games so you can manage training and gameshape minutes.
Squad Nationalities; Is there a limit / requirement for how many foreign and domestic players are allowed in a squad/team?
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You can have as many foreign players on your team as you want but you'll get more merch money for local players.