Social Media Tip: Be a part of the community
I hear a lot of 'I need a lot of followers to get agents interested in my book.' While I do encourage my clients to get involved in some form of social media, you don't need hundreds or thousands of followers in order to be 'publishing material.' Becoming part of the writing community, and what all that entails, will be beneficial to you, too.
I have learned over the years the best way for a new writer, editor, etc., to join the writing community is to follow hashtags related to you and your writing, join those hashtag parties, follow people who offer advice, follow authors you love, and interact with people who are new writers, as well. I also recommend to really look at the authors you follow, see what they do that adds to the community. Make a list for yourself and mirror your social media with that inspiration.
The more authentic you are, and the more you add to your connection to the community, the more followers you'll gain over time. You should definitely do self-promos for your book! Also, be sure to give back and add to the community, such as with helpful resources, encouragement to other writers, or whatever you feel that is a useful contribution.
And you don't need every social media platform. Pick one or any that you feel works for you. This means, if you do better with aesthetically-pleasing pictures rather than long worded posts, then Instagram is for you, and so on.
Building a social media following as a new writer is not about the numbers. In the end, agents and people who are truly interested in what you do and what you've done won't necessarily be looking at your numbers. It's about finding your community and creating your unique way of contributing to the conversation. Just be YOU. Remember, even done well, it will take time.