You're missing a lot of jobs from sidequests, which would probably help a lot. Any blue ! on the map is a sidequest you can do, which will give a new job. I think you could potentially have Time Mage, Spell Fencer, Ranger, Swordmaster, Pirate, Salve Maker and Vampire by now.

Since you have Dark Knight, you must be in at least chapter 5, and so your level is actually really low for this point in the game. Normal level around here is more like 55-65, so 47 is very low. And considering that, I'd say you're doing fine (assuming you're playing on Normal or Hard anyway).

In terms of job combos, mostly you want to make sure you level a reasonable mixture of jobs. At this point in the game I'd generally like to have about 4-6 jobs at level 9, and have at least one job on each character I want to push towards higher levels. I'm not going to suggest specific combos, since it depends a lot on how you want to play, but basically yeah, try and experiment and work out what's working for you. It's hard to get straight 9999's at the moment, heck, most combos don't necessarily reach that ever.