What palette to choose?
Palettes are a delicate matter. So what are we looking for?
Since watercolor is intimately connected with water, any non-absorbent surfaces with edges will suit us in the first place. And they must be white. Can you guess why? It's because we are dealing with paints. Any colored background will distort the color of the mixtures.
If you are just starting to paint, it will take time to choose the right tools, so to start painting, use whatever is at hand. Any white plate from an old set, a flat enamel tray, a plastic lid from a children's set, a piece of white ceramic – anything can be used. The most important thing is for you to be comfortable mixing. It's important that whatever you choose as your palette is white so that you can understand what shade you've achieved and so that the paint doesn't spread.
When I started painting, I had several small metal boxes from candy in my bag, in which I squeezed out a few favorite paints. And to this day, at home, I use a lid from an electrical cabinet.
Different artists use different palettes according to their needs. Some are satisfied with 12 cells, while others need 30 or more. Some squeeze out paint for one session, while others squeeze out a whole tube onto the palette at once, so they don't have to worry about it later. There are artists who use porcelain sauce dishes (Sergey Lysy), and there are those who adapt a surgical enamel basin (Anna Ivanova).
But what if you want something more serious?
It is considered that the most convenient and budget-friendly palettes are the small Mijello ones for18 colors. They are compact, tightly sealed, and if you paint often, the paint in this palette won't dry out. They are also not bulky and can be taken outdoors.
Of course, there are countless options on the market, there are palettes of different sizes, but I recommend starting with this model. With experience, you will understand what you need for all possible cases.
Summary
Choose a white palette made of non-absorbent material, and it's desirable for it to seal tightly. With experience, you'll find the most convenient option for you.