You always take out the highest loan you can afford casul. The sooner you invest into your buildings the sooner the cash starts flowing for exponential growth.
You have to do the early shareholder bossfights with -10 on capital, due to your massive debts, but you will become immensily rich.
The management minigame is fun, and there is some "post game" content for it. Getting the number 1 slot unlocks new business ventures and employees and stuff. But I don't think it has more than 5 hours of entertainment in it. It is just a fun time waster for the slumdog millionaire feeling.
You can unlock it in 1-2 hours of playing or so, no need to download a save. You need to complete it for the 5th chapter because there is a fairly large money gate there, that you are supposed to pay off with your manager bonusses.