In my opinion the best level is marginally less than you can afford (and by "afford" I mean play long losing sessions every day for a week and still be afloat)
If you go too high, you will play too conservative, or get too annoyed by loses.
If you go too low, you will play too aggresive and not be satisfied by your return.
I only ever consider this, and not the standard of the competition, because losing runs & awful bad beats will happen at all levels regardless of your ability.
Have Fun, Welly