Being a promoter you can do simultaneously because it doesn't need a long time to make a thread/review/comment or everything related to it. But you just need a broad knowledge, don't you forget there are a lot of project who end up in scam so as you need to know it and you have to make an analyst when you choose a project.
I know fully well life is all about risk but its better to learn something's from other persons experience with the respond here I can say that I can go for both Marketing/Promotion and Trading at the same time. I know too much questions is not to good but it has really helped me a lot. I will kicked start as soon as possible.