GYMNASTIC RINGS
We highly recommend this eBook by PT James Lee to "provide you with the basic tools that you need to build a solid foundation of movement and control through several key positions from which to develop these more advances skills safely and effectively."
The scope for progression is enormous and the journey to the high-level gymnastic skills is one of years, rather than months.
However, anyone can use this equipment to build muscle, strength and skill whether you are training at home or in the gym and most will be able to achieve a relatively high level of skill should they wish, no matter your age or start point.