Christmas Is Coming...

And I want to dualbox. I'm finally going to have a computer that can do that. Right now I am playing on a weak All-in-One PC that barely plays a single account. My question right now is:

If I make a second account, I want to supplement my main account. What are the best job combinations? Should I make a RDM? Or a GEO? Or BRD? My mains are COR + GEO + DRK, but I have space for one more job? Should I make NIN? Or THF?

I'm curious what two jobs pair well with each other for solo'ing purposes. All b/s aside... I will never elevate to 3/4/5/6 accounts, just looking for opinions and information on how far I can go with dualboxing!