Left hand Rythmic patterns

[drooxy]

Hi everyone,

Could someone help me find some simple and various left hand rythmic patterns in different styles ?

I would like to try to:

1. play these patterns in all keys and through different
   chord progresssions (I-IV-V, II-V-I for example...),
2. practice some right hand exercices, scales, melodies,
   etc. over them.

By the way, what keys - out of the 12 - would you suggest to be the most important to master (because they are the most common OR because, by mastering them, we can be at ease with some others for similarity reasons OR etc. ) ?

Thanks really in advance !

Drooxy