Twitter is a different animal than Facbook or Goodreads. IME it's an acquired taste and not everybody's thing. It's sort of like being at a cocktail party where everyone's talking, but not necessarily to the person standng next to them. Personally I really enjoy it, but it took me a while. (Whether or not Twitter sells books is a different question, and I think the answer's different depending on how you're published.)
Your tools are searches, follows, likes, retweets, and hashtags. Here's one potential getting-started method:
- Follow some people you know and/or like: friends, authors, celebrities, journalists, etc.
- Like and retweet things you like and want to share.
- Comment if and when you feel like contributing to the conversation. (It's common for no one to reply to you - Twitter is often a read-only experience.)
- Search for topics that interest you. (Twitter uses hashtags, like #InfinityWar, but you can also search for general keywords. Once you see the common hashtag used, you can search on that and use it for your own posts.) Like and retweet posts there that interest you.
- Follow users who post things you enjoy/find useful.
Hashtag games can be useful for giving you concrete things to post about. There are some, like #authorconfession, where there's a daily question and anyone who wants can answer it using that hashtag. This will find you more people with common interests, and it'll help them get to know you, too.
Over time, you'll find that liking, retweeting, following, and tweeting yourself will get people to follow you.
One trap you want to avoid is becoming the "Buy My Book!" tweeter. This doesn't mean you never tweet buy links to your own work, but make sure you tweet other things as well. There are people who tweet nothing but Amazon or Patreon links. There are people who'll follow you, and drop you if you don't follow them back. Don't be that person.
One way to talk about your work without being Pushy Sales Person is to talk about it while you're writing it, or (if it's finished) some of your insights into the process. Share like you're talking to interested acquaintances, not like you're in a marketplace. You do not EVER have to get personal or revelatory, but sharing little bits of your personality is more likely to get you "sticky" followers.
TL;DR: Follow people you genuinely want to follow, and contribute to the conversation at your comfort level. Building followers can take time, but it'll come.