Lots and lots of variety! I have found that–after being a long-time MAC user–variety is important. It helps you learn what you should expect in products, what really works, what doesn’t, and what’s worth it. I don’t have something from nearly every brand, but there is definitely diversity in the products I have.
I think the color is most important – sometimes high-end brands do seem to put out interesting takes on color. I don’t get better or longer wear out of a high-end polish over something cheaper. Rescue Beauty Lounge and Butter London have really exceptional formulas.
If I’m just hanging out, then I’ll opt for tinted moisturizer, waterproof mascara, and maybe a wash of eyeshadow. I’ll avoid gloss and go for a lip tint or lipstick, because I’d rather not have sand stuck in my gloss!