There are lots of tank options out there. I definitely recommend using a tank on the Provari for an all day, hassle free vaping experience. Whatever type you decide to go with, I would suggest the 3 ml size. Here's a breakdown of my own experience.
The Jonboy lava tank: My personal favorite. Looks fantastic, easy to fill, provides and excellent vape. If I had my way, this would be the only tank I would use. Unfortunately, these tanks are difficult to come by because they are individually handcrafted by a real person who seems to have an actual rl outside the vaping world.
The Liquinator: I really like these tanks. I have a SS and a delrin which I purchased early on. I felt these were easy to fill, provided a good vape, and I've never had any leaking. There were a lot of people on the forums who complained they were too "slidey" though. I personally didn't have a problem with that, but the company apparently listened to what customers said and started making them fit the cartos tighter. I ordered a couple of the aluminum ones later, and imo they fit too tightly. They are starting to loosen up some now, but when I first got them they were extremely difficult to fill.
The Mini-Sub from Mom & Pops: I ordered a couple of these recently to use temporarily while waiting to acquire some tanks that are more difficult to get. The best thing about these tanks is their price. They are very inexpensive. They work well and have a fill port so they are easy to refill. They also vape well, can handle my cv drip tips, and don't leak. My biggest complaint with these is that it can be difficult to change out the carto.
I will be receiving a Phideas frosted tank and an ACTv4 this week. The main reason I ordered these is they are immune to cracking. Some liquids like cinnamons and citrus flavors can cause the polycarbonite tubing in other tanks to crack. I've never personally had this happen (knock on wood), but I am careful about what liquids I use. I have also heard an awful lot of good things about the Lil Mama tank. I know you can also buy glass tubes that will fit the Lil Mama so that sounds like a good option.
As I mentioned earlier, there are plenty of tank options out there. As you can see, I am a huge tank fan and would highly recommend anyone using a Provari to explore the world of tanks.