First of all, I would decide on an instructor, and then through his website or through communication with him, you can find out what gear you need to bring, and what you can rent or what is provided. You can also find out if any gear is specifically to be of any certain type or configuration.
From two years of being down there, here are my recommendations:
If you have done or can do GUE Fundamentals, take GUE Cave 1 with the Zero G guys. The quality of the classes is absolutely fantastic.
If you are not interested in GUE, I'd recommend Dennis Weeks of Aquanauts, based out of Puerto Aventuras. Dennis is a very nice man, a dry caver and cave diver, and enjoys an excellent reputation. My husband has done guided cave dives with Dennis, and was very pleased with him. There is very good lodging in PA (contact
debbie@diveaventuras.com to talk about options -- she's done very well by us) and there are restaurants in walking distance. PA is also quite close to the fill station.
Another option would be German Yanez of Yucatech. German lives on Cozumel, but is willing to teach on the mainland. German was my instructor for my Cavern and Intro classes. He is an extremely pleasant and patient man, and very good if confidence is an issue for you (as it was for me). He has a long track record of cave exploration and survey. If you choose German, you can say in the Playa del Carmen area, which will make an all-inclusive an option, if that appeals to you. (Come in the off season, and you can get some very good deals at those places, but the food is pretty bad.)
Please feel free to PM me if you have any questions, or want any advice on logistics.