When you have 0 gap(your level is same as your mastery level) you get 100% exp and 100% sp exp. This is the fastest way to get lvls but you get very small amount of sp. When your level is different then your mastery lvl, for example your lvl is 15 and your mastery lvl(bicheon,fire,warrior,wizard mastery) is 12 you have gap 3. This gives you little bigger amount of sp but lower exp so you will lvl up little slower. The biggest gap you can get is 9. That is the best gap for farming sp but it is the hardest to lvl up. Because you dont have skills your lvl and you are weaker, also in euro classes you cant wear equipment your level. It would be probably the best to get pfarm at ongs with gap 9 or if you want you can go with gap 3-4 all the time.
This is how exp and sp exp goes with gaps:
0 gap = 100% exp, 100% sp exp
1 gap = 90% exp, 110% sp exp
2 gap = 80% exp, 120% sp exp
3 gap = 70% exp, 130% sp exp
4 gap = 60% exp, 140% sp exp
5 gap = 50% exp, 150% sp exp
6 gap = 40% exp, 160% sp exp
7 gap = 30% exp, 170% sp exp
8 gap = 20% exp, 180% sp exp
9 gap = 10% exp, 190% sp exp.
10 gap = 10% exp, 190% sp exp.
So above cap 9 it is same like cap 9 so keep cap 9 as your highest cap.
I hope you understand thinks better now
