I would recommend the Provari. If you get something like the less expensive Vamo, make sure it's the V2 (or whatever it's called) that has the 2c safety stuff better worked out.
I really don't understand the "stage" thing unless one has already done it because they didn't know better, and then in hindsight can say 'yeah, that's how it happened'. Looking forward from here, there's no inherent reason anyone has to graduate from Blue to Volt to Ego to Lavatube to Provari or Zenesis iHybrid or whatever, spending money on each step of the journey.
If you can discern how you like to vape and what features you need, then go for the best device you can afford, or possibly beg, borrow or steal to get. I can see, for example, why VW might appeal to some people, but since I'm a one vape person, I only need a single, regulated voltage, and what the VV on the Provari does for me, essentially, is enable me to use use any Ohm resistance carto/tank/atty and adjust to that same vape. So I don't need anything else.
And not to come across as the proverbial Provari fanboi (though I have become one), but I've read so many reviews about the cheaper devices that work fine until the the button gets stuck, the cap threads get shredded, the finish corrodes or the circuitry shorts out. Or you read that the volt/Ohm readings aren't very accurate and the button action is inconsistent. Why bother cycling through all of these permutations until you end up splurging for the device you really wanted all along anyway?
And no, I'm not saying that all of the $40-$80 VV/VW mods out there suck. What I am saying that if you really want to do this, definitely do your homework, because the quality control issues are all over the map. I decided to skip this issue entirely by just getting a Provari.
I purchased 4 various ego batteries with extra attys and cartridges a month ago that I no longer ever use, though all is not lost because I can use them as backups or give them to friends. I also have a Provape-1 that I will seldom use, not because it's not VV, but because it's unregulated, though I am thrilled to still have this as a mechanical backup. But in retrospect, I could have just skipped the Ego stage and saved a little time and money.
So just get a Provari. That's my 2p.