Having used Leica 'M's' for thirty years I wouldn't recommend my favourite type (M2) to somebody new to the system.

Essentially as a new user you want two things in a Leica M, a meter, and as many framelines as possible. A meter so you have some comfort during your learning curve, and framelines so you can discover and experiment and find your own rangefinder vision. An M6 TTL or an MP would be ideal, and the M6 has a slightly faster rewind action. When you get used to the camera, the lenses, and discover your most used lenses, then you can perhaps buy a less versatile but more 'focused' M body like an M3 or M2. But a lot of people like to keep their main camera as the versatile one, there being no great virtue in limiting yourself unnecessarily.