macrocephalopod

First important thing is that VIX futures give exposure to forward VIX, not VIX itself. You can have a correct view of where VIX is going but still lose money trading futures, because the futures price already includes market expectations of where VIX will go.

so if e.g. VIX is 20 and near-term futures are 23, to open a long position it's not enough to believe that VIX is going higher -- to make a profit you would need VIX to go above 23 *within a month* of you opening the position. If it goes to 22 you still lose.

In this example you lose 0.1 = (23-20)/30 of a VIX point every day, assuming that the term structure doesn't change. This is called *rolldown* and it's necessary to understand it if you want to trade VIX futures.

It's not sufficient though! There are many terrible "VIX carry" strategies out there which go long when rolldown is +ve (curve is backwardated) and short when rolldown is -ve (curve is contangoed) and ignore predictable movements in spot VIX.

Spot VIX is not tradable, which means there is nothing which stops it from being predictable. To profitably trade VIX you need to know what the rolldown is and *also* have a good model for how prices are going to change.

To model this you should build constant-maturity VIX curves by interpolating forward VIX prices to a floating grid of expiry terms (e.g. 1 mo, 2 mo, 3 mo) rather than a fixed grid of expiry dates. You then build a model to forecast the changes in constant-maturity forward VIX