1. You're going to have to figure this on your own OP.
2. You can manage a couple of accounts
The reason he is saying that is because it depends on the content you produce and how you target your audience. If I told you that I have huge gains from the fitness niche and you just go out and spam fitness stuff you will not see results. If you know how to target your audience you should get reasonable gains in any niche. Just pick a niche that you understand.I was asking your opinion. How am I going to figure out your opinion?