Teacher here who sets up classroom kits. Main thing is balance between quantity and quality. Many budget sets are fine for learning as long as they are not watery and they dry to an even film. Do a quick test if you can on scrap paper. If the color looks strong with one or two passes and it does not rub off when dry you are in good shape. Big help.
Transparency matters. Get at least one opaque yellow and one opaque red because early layers are less frustrating when they actually cover. A cool blue that leans toward green and a warm blue that leans toward violet will make mixing easier. White disappears fast so larger tubes save headaches. Skip huge assortments packed with odd shades for now. Add a few targeted colors after you figure out what you keep mixing.
