First things first, I state that I'm not a master at this in any way, just been playing the mode for the last couple games and had a bit of advice. when you get asked by the press about what your goals are as gm, the best answer (IMO) is "multiple championships". This will get you a good amount of press trust (easier questions in the future) and boost the morale of your team and staff. You lose on owner trust but by completing promises you can get it back.
Don't be afraid to reject players when they ask you to do something. Their morale goes down by 3 and you can easily get that back in a few wins. This often comes up when you're adjusting training and they want harder training when they're already at the max.
Speaking of training, first thing you should do is set training to very high on your reserves and deep bench players. This will get them good stats in the long run and they'll rarely become tired.
Another thing about training is that they aren't kidding when they say a player is "sluggish". Resting your players and not overworking them is what makes you win games. The fresher they are, the more wins you will get. The issue is that you probably won't get much stats for next season in return.
If your owner makes a promise to keep team chemistry over a certain amount, NEVER TRADE A PLAYER. YOU WILL FAIL IMMEDIATELY. Unfortunately I haven't found a good way to trade a player without having the chemistry fall back down to 60.
I don't have any tips on buying a franchise because unfortunately Ive never been able to get the 50k VC for it.
I recommend seeing other people's tips as well because I am far from the best at this mode. Just go out, experiment, and never be afraid to make a new file if things don't go well (you have 100 spaces anyways.)