Welcome Kuljit, but the first thing you need to do is tell us what you got! What color Provari and LED? Mini or full size? Any accessories besides batteries? What mod are you upgrading from? As well as sharing your excitement with all the details, we can give better advice understanding a bit about where your coming from and where your headed vape gear wise. But mostly, we're just a bit nosy that way.
Don't sweat charging the batteries first, they will come with at least a storage charge and be at 3.7v or higher. So you can charge one while you enjoy your Provari with the other, and when the first is charged just switch. Besides the Provari is pretty smart and won't let you drain your battery to a point it's damaged, so no worries there.
Tanks are really personal and hard to recommend without knowing your preferences a bit more, but if you like your Kanger, you can keep your Kanger (sounds like a lie somehow

). If your Kanger gets enough airflow from the 510 connector it will work great, if the air is a bit tighter than your used to you could try unscrewing just a bit to get air while still maintaining electrical connection through the 510, or get an AFC base. Any 510 connection tank will work if it gets air flow, so do some research on what tanks looks interesting to you.
Welcome to our world, not a bad place to be.