wat if i want to farm in lvl 18, wat lvl of skill do i need to put

like people say farm on lv 16, i have to keep skill at lvl 7

farm you need: gap9.
Ej: you are lvl 19 and mastery lvl 10, you have gap9.
You are lvl 19 and mastery lvl 0, you have gap9. (max gap is 9 = 90% exp sp and 10% exp).

You max can lvl mastery in 9 if have lvl 18.
But if need farm +50k sp, you need down lvl.

oh got it
thanks alot bro