I find that different jobs level best in different ways. When I play CNJ, for instance, I find it's much more fun and much faster to play with groups. Any groups you can find for your level really, Shposhae groups (they do exist, sometimes!!), general exp kill-lots-of-mobs groups, Toto-rak Dungeon groups etc.

When I play PGL, I find soloing to be a lot more fun, and I do levequests and farm in Sphoshae and stuff at lower levels.