Hey fellow pso-world members, I seek some advice from fellow members who have gone through the GAS system already.

I want to try to get the Master Force customization, more specifically the limit breaks. My question is though, is it better to get the AEXP from /R missions or just wait till I reach 180 (currently 121). If so what class is more viable or more helpful for the /R missions? since Master Force can't equip any armor without any customization. Any general tips are also appreciated.
Thanks in Advance.