There are all sorts of reasons why you might choose one yarn over another. Your budget, your values, and your needs all influence that decision—and those are all valid factors to consider. Whatever yarn you choose you’ve made the right choice for yourself. You know your own needs. In other words: this post is NOT the place for yarn snobbery.
Technique matters more than yarn choice. If you want to help your project look its best, think about your stitch tension and what you can do to keep it smooth and even. If you struggle with tension, think about what contributes to that. Is it your needles? Do you struggle more with certain yarns than with others? Does your mood, stress level, or environment affect it? Use that self-knowledge to your advantage.
Whenever possible, I strongly recommend using a yarn that has at least 50% natural fiber. My favorite is wool, but you might also want to use alpaca, cotton, linen, or other animal or plant fibers. I like wool because wool has memory, which helps keep knits from getting saggy and misshapen as they’re used. That memory will help your knits look polished longer.
When you’re done with a project, you should soak it, gently squeeze out the water, and lay it flat to dry. The reason this step is so important is that it relaxes the natural fibers in your yarn. That helps the stitches to settle into place and smooth out.
I’ve talked about photographing with natural light a lot on here, so I won’t go into too much detail now. Suffice it to say you should make sure to use indirect, natural light with a neutral temperature. You don’t want light that’s reflecting off of a colored surface or coming in at a harsh angle that casts shadows.
I like to use things that are both beautiful and functional. Part of that means I’ve got a nice little stash of dishes, trinkets, and flowers around to use in my photos. When I photograph my projects, I add those pretty things as props to create the atmosphere I want. When you add things that are special to you (and match the mood you’re trying to evoke), the budget yarn will seem elevated by association.