Well, I guess I'd analyze it this way: You ARE currently diving. You might dive more with your own equipment, but you are diving already. Whether you are diving your own equipment or rented equipment, you may well encounter problems of your own, or someone else's, during a dive. So the skills you learn in Rescue will be useful, whether you are using your own equipment or renting. On the other hand, having your own equipment, running into a problem (your own or someone else's) and not having the education to deal with it effectively, would be stressful and potentially injurious.
I'd spend the money for Rescue, and then save up for your gear. JMHO.
I don't have a high opinion of my mainstream diving education (OW, AOW, a bunch of specialties and Rescue) except for the Rescue class, which was excellent, and which I would recommend to anyone.