There are two general gouache price points, affordable and expensive. With affordable gouache paints, I get the look and feel I expect just not its full potential.
Gouache paint consists of pigment suspended in a binder, usually gum Arabic, just as is watercolor. However gouache has larger particles and more pigment in its binder. It also includes an inert, white such as chalk. These make gouache heavier, more opaque, and more reflective than watercolor. The extra pigment and whitening with the longer mulling production time adds to its cost. The price is even higher for true pigment colors compared to similar manufactured hues. Cadmiums and Ultramarine blue the most expensive.
Many scribes begin with the Reeves 24 tube set. It has more hues than you need, but I think you have more choices similar to common Medieval colors. The affordable price ($15) is due to most colors being cheaper pigment combinations used to make a hue and the limited pigment in the binder.
I prefer Winsor and Newton paints, but have used them together with cheaper brands. I pay more, but prefer the quality results. The finish seems less streaky and the colors are more brilliant. The cheaper paint may also fade quicker than the expensive kind, but that is only a worry if the illumination is kept in full sunlight.
If you are a beginning scribe Reeves paints are a great way to learn paint application and color mixing while you create pleasing scrolls. As you run out of a color replace it with a similar artist grade designer gouache color. Little by little you will have the colors you most often use. Unless, of course you spring for a color you can't live without, like most of my collection.
Related Prior Post:
Why Buy More Scribal Paint Colors?
Gouache and Watercolor Paint Comparison