A lot of variables can make for a different answer to your question.
What do you currently use?
How large do you want your battery to be?
What do you feel like you are lacking that VV will make up for?
How involved do you want to get with the whole experience?
I am only about 7 months into vaping but have tried many things in that span. Started with cig-a-likes, needed more battery life. Moved to eGo batteries and loved them, but wait.... I needed variable voltage. But why? Truth is- I own 4 spinners and have no idea why. They are never dialed above 3.8 volts when they get used. But why? Because I prefer to use low resistance equipment. I prefer warm vapor with a nice cloud, which -for me- can be achieved with the correct ratios in my liquid and low voltage like you would find in a standard, non-VV eGo battery or mechanical mod (my new found love with 1.2ohm coils).
I tried dual coils, high resistance cartos and atties, higher voltage, different liquids, higher voltage, lower voltage, burned some cartos, so on and so forth. And after all of that, what do I vape daily? A dinky little eGo 650 batt with a low resistance coil in my tank. I get everything I want for a super good price and don't need to worry about keeping a spreadsheet for which liquid tastes best in which device at what voltage and how it all factors into the lunar cycle.
Long story short, I have spent many dollars on variable voltage without even knowing if it was what I needed and, as it turns out.... It wasn't.
Of course, as I mentioned- the answers to the questions above will paint an entirely different picture for every person, so it boils down to knowing what you would like to achieve without having to go crazy with VV fever. What you are looking for might be found in something as simple as the ohms in your coil.
Sorry for the winded post. That would be my .04 LOL