No one can really answer the question "what size needles are best?" because every pattern is different.
When I first began knitting, it was with a little mother-daughter knitting club that a friend started up. She chose a project that we all agreed on...and I bought the appropriate needles for that project.
As I learned to knit, I searched for various patterns online...and every pattern seemed to call for a different size needle. I finally decided that rather than limit my pattern search to "Patterns that use size 8 needles" or something similar, that I would just invest in the KP Options set (there are a number of similar interchangeable setes), and just have what I needed onhand. It was much cheaper than buying individually the needles in the various needle sizes and cable/cord lengths every time I started a new project.