There are lots of good juice vendors and we all have our favorites. I have several vendors I use. My favorite is Heather's Heavenly Vapes. They are very clean burning juices too. Some of the flavors a Silverthorn enthusiast would like are..
Dragon's Fire
Heavenly Army
Shadow
Legend
Huntsman
Serendipity
others
As far as a tank, I would go with rebuildables but it sounds like you might be a bit new to the vape experience so I would work your way up to those. For now, your Vivi Novas will work fine for the 70/30 (PG/VG) juices. If you're going with the 100% VG then I would go with a bottom coil like a Kanger Protank (clean and dry burn after every 2 or 3 tanks). VG is significantly thicker than PG and a bit tougher to wick. I believe someone else recommended the Protanks above and they would be right.
Heathers Heavenly Vapes, Top Quality Custom E-Liquids