B.o.b is all depends on your account status. I have been botting agility on my level 3 for 2 or 3 days and its already level 60. If your level 3 do barbarian basic with cakes. Remember to keep getting food!! If your a pure or main, do the ape atoll course.
I would actually suggest since you are quite low to not attempt Ape atoll or the Wilderness course, rather, you should do the Gnome agility or Barbarian Basic course, I can't remember which is best experience (Barb I think)