I will recommend a MR-02. it's easiest to play and set.
MR-015 is just for fun, not running quite as fast as 02 or AWD can ( due to high CG, very easy to flip over at fast / tight corner )
Up to this moment, 02 and AWD is most suitable for serious player. A lot of hop up and setting available. Both 02 and AWD can be very expensive if you want to highly modify.
I will recommend a MR-02 with Atomic 20 / 10º tyre, and ball diff will also be a very good first modify.
As For Starter i will suggest buying a MR02 it should be about the same price as a used 015 as well setting car or everything is more easily plus we can play together^^ i got poison long ago ........ no cure