The Raiden is a great flying, RTF electric glider. A guy in my club used it for a lot of the basics of learning to fly. I also second the Easy Star, though the Easy Star isn't a very efficient glider and doesn't thermal very well at all. When I feel like just floating along with my Easy Star, I keep just enough power on to turn the prop, 2-3 clicks of throttle. This helps offset the drag just enough to allow me pretend that it has an efficient glide

The only draw back is that there IS a big jump from a 3-channel glider to most conventional powered planes. Basically you wind up moving up to what is almost a primary trainer next anyway, so if you have a good instructor and buddy box rig, you can save time and money by just starting with the primary trainer.

Of course that assumes a "goal" of wanting to fly powered models like warbirds or aerobatic planes and so on. If that's not the desire, then who knows, you may find gliders to be your "thing", and you may go from a basic intro powered glider to one of those amazing high performance gliders (with some steps in between) and so on.