Rather than buy a full set of one type needle right now, why not buy just the needles you think you'll need for the current project? That way you can try a different length or type of needle for the next project, maybe a circular or ones made of metal, plastic, bamboo or wood? There are lots of options and experience will help you decide which you prefer.
Here are a couple of sites that describe yarn weights:
Ravelry is free to join and Knit Picks is a good, inexpensive source for a variety of needles. The beginning is always a great time in any project. Welcome to Knitting Help and enjoy!