The Cricut Explore Air 2 is the next most cost efficient machine, and much larger than the joy. It's great for cutting any potential shirt design, but isn't Smart Materials compatible like the new machines.
The Cricut Explore 3 is the newest Cricut model, and is Smart Materials compatible. The Smart Materials are great for making repeat designs for multiple shirts.
The Cricut Maker 3 has all the capabilites of the original Maker and Explore; with the added bonus of being Smart Materials compatible like the Explore 3.