I have already written about the needs of customers, now let's talk about specialists. First of all, you need to know what kind of SMM you would like to become. Content manager? Targeting specialist? A blogger specialist? Administer a public? Or maybe design for social media?
Even if in the end you want to be able to do everything, everything, everything, in the beginning it is better to choose one niche and upgrade in it, and then slowly attach new skills to it. The same advice applies to skills in specific social networks - start with one social network, understand it, and only then learn to work in other social networks. This will be more correct.
At the stage when you enter not only to perform tasks on the technical assignment, but also to offer your options for SMM strategies, content plans, and so on, you will need good knowledge in marketing, otherwise you will understand how individual tools work, but you will not have shared vision.