How much white gas should you bring on your trip? That's actually going to depend a lot on your style of cooking, your stove, the conditions, The white gas stove I've used the most is my MSR Whisperlite. I'll be using my experience with my Whisperlite to generate the numbers that follow.
A word about style: On most of my backpacking trips, I keep cooking fairly simple. Most of the time, I'm boiling water for re-hydrating foods and making hot drinks. I almost always have tea in the morning and cocoa in the evening. I normally boil at least two cups and more typically three cups per boil. Simmering for the most part is kept to a minimum, but I do simmer sometimes to re-hydrate things at higher altitudes. I don't typically have a hot lunch, but I almost always have a hot breakfast and supper.
Over time, I've noticed that I use something on the order of 1.5 fl oz (44ml) of white gas on a solo trip per day. For two people, I find my usage is something on the order of 2.25 fl oz (67ml) per day. If I'm melting snow, I figure on roughly doubling those amounts. These amounts include fuel used for priming. These amounts are the amounts I expect to use. Particularly in winter, you should plan for the unexpected. I typically bring an extra day or two's worth of fuel on winter trips.