If you're new to Mastodon and the Fediverse, welcome! 👋
You can find people to follow at these places:
https://communitywiki.org/trunk - A community-built, opt-in directory of people looking for followers
https://mastodon.online/@FediFollows/106855947486154929 - A manually curated directory of intresting accounts that generally focus on single topics or themes (and you can see the latest entries by following @FediFollows)
There are millions of people you can follow on here, but the above are good ways of getting started.
You can find even more people by searching for hashtags, and make sure you include hashtags on your own posts so that they can be discovered more easily.
Also, post a short introduction about yourself with the hashtag #Introduction