what level should i play vs Machine

What level should i'll be able to beat or should i play depending on my ratings?

1200 AI 1
1300 AI 2 and so on

Just play other ppl!

Probably AI 5 or AI 6.

Play each level until you get to one you can't beat, and that one you can't win against is the one you should play. Make a point to play against real people as well though, there is a difference.

Play anyone