It depends, and you'll get as many preferences as there are painters. It also depends where you are.
First, in which style are you painting--matte or gloss?
For matte, I use Tamiya water-based enamels, as well as Model Master acrylics, and Testor's, and I also use the cheap (under a dollar a bottle) craft store water-based acrylics.
For gloss, I use the gloss enamels and acrylics from the same manufacturers. I'll also use matte colors, and then coat the figure with Future floor wax, which is a liquid acrylic clear.
I also use Mussini/Schminke oils for some things, as well as Gunze-Sangyo paints, and I still have some old bottles of Pactra enamels.
Humbrols aren't as readily available here in the States as the brands I've named, though they can be found, of course. I have a couple of bottles of Andrea's water-based acrylics, but for my purposes, the craft store acrylics do the same job, so I refuse to pay Andrea and Vallejo prices for something that works just as well for much less cost. That's why I use Future for my gloss coat, too, rather than buying something from Testor or Tamiya. I do use Testor's DullCote, though, because I haven't yet found a cheap alternative that works consistently.
Also, as you go along with painting, you might learn how to mix colors--I'm not so good at it yet--and you'll find you don't need to buy a specific "WWII Color Set" or something similar, such as Andrea packages. You can buy some basic colors and mix them yourself.
Regarding what I've said about cost, I'll add that I follow the principle of frugality. Frugal doesn't mean cheap--it means you don't waste anything. So, I invest in good brushes, for example, which will last longer, with care, instead of buying cheap brushes which will wear out and have to be replaced frequently. You wind up spending more, in the long run, which is a waste.
Hope that all helps, and let us see what you're painting!
Prost!
Brad