Shopify uses Sorbet and a few companion projects (e.g., Spoom¹ and Tapioca²) to manage Rails projects of various sizes. While there are some holes, like you find with any gradual type system, I think you'll find the experience is quite good. The awesome-sorbet³ project has a comprehensive list of blog posts, conference presentations, and podcast episodes that dig into that deeper.
¹ -- https://github.com/Shopify/spoom
² -- https://github.com/Shopify/tapioca
³ -- https://github.com/andyw8/awesome-sorbet