When I started DPN usage, I purchased a set of bamboo in the size I was using. As I got more familiar with them I switched to steel needles. I never use plastic because they drag on the yarn. Wood and bamboo drag also, just not so much.
I'm currently using Hiya Hiya brand needles a lot because of the low price plus low nickel in the finish. I almost always use circular needles for flat knitting. No ends to catch on things plus lighter on the wrists. I use DPNs for small circular projects and circulars for larger circular projects
Welcome to knitting!