It’s a little heavy, but I can say it runs fine in a 1 GB VPS, with the addition of a 1 GB swap file to compile the front end during installation and upgrade.
I'd go a little bit further here: I run Mastodon on a 1 GB VPS as well, but I found I had to make the swap file permanent to stop it from running out of memory. It's not super heavy but it is heavy, and even though swap is slow, it still runs fast enough.