You can use dual coils, but most people use single coils. As for tank options, there are many. Most people start with:
The Kanger ProTank 2. Recent batches from Kanger have had airflow issues on the ProVari, and so people that use them have also purchased
The Aero airflow base or just switched over to the Kanger Aerotank entirely.
Others choose to go with punched cartos and cartotank setup. There are many different cartotanks out there, but most people use IBTanked cartotanks
If you want to start using rebuildable atomizers, the Kayfun Lite + is one of the best choices out there, though it will look slightly strange on a ProVari unless a beauty ring/pro ring is also purchased to give a flush look to the ProVari/Kayfun combination.
I've listed only the most popular combinations...anything with a 510 connector will work on the ProVari, and if you prefer clearomizers, MT3's, or Evods, a 510 to Ego connector will let those work on the ProVari too.