What is the most practical pan for a deep-dish pizza
A 2" or 3" deep round cake pan (i.e., fairly thin aluminum, but nowhere near as thin as the disposable things) actually works pretty well. These cost under $10 each. For example, Walmart sells one for $9

That's a 9" wide pan, but 12" cake pans are available too—and only a little more expensive. Maybe expect to pay $15 for one.