How can I add a 30 amp breaker for an RV connection?
You're in luck -- your panel can accept another 240V breaker in the bottom knockout pair.  You'll need a 30A Siemens type QP breaker to install there, which you can pick up at a typical big-box store.  (A GFCI is not needed here, best I can tell, because this is a single outlet in dedicated service.)