Do You Have To Use Textures On Low-Poly Models Or Are Materials Enough To Give Them Detail?

Can I just use materials to ‘colour in’ different parts of my low-poly models rather than going through the process of UV’ing and texturing them?

It all depends on what look you’re going for. I personally like the low-poly, no textures look, but obviously textures can add a lot of detail and you can do cool stuff like bump/normal mapping if you add UV coordinates.