you dont have to make all your skills 0 gap
just chose whatever your mastery is.
even only 1 skill with 0 gap like your level
is counted already as 0 gap.
it doesn't have to be all.
what i did is i never farm at all till level 89.
i am now lvl 87 with 0 gap coz you can still level ur skill till 90
just for high exp and as soon as i get to 90
i will delevel back again the skills i dont need.
thats all..you dont need to farm in it coz it has a high exp/sp rate.