if you are farming at ongs with 9 gap you will not only gain sp.. also exp ofc
and if you are like 30 you will not gain that much skillpoints anymore so you can move to hotan to the flowers outside and die die die die.. (with a cleric who will ressurect you ofc) until you are like lv 20 again and then you can go on farming at ongs with much more skillpoints each ong