What is the best career choice for a social psychology graduate?
In general I would counsel against further study. I have seen many people finish an undergraduate degree, look for a job they like/a job, and when they have no luck go back to study. This has almost always ended badly. In most cases they have no understanding of how a further degree will allow them to get the jobs they are interested in, and are merely spending a lot of money to prolong (or make worse) the problem. 

If you are incredibly passionate in an area go for it. However the fact that you are posting this/reading this suggests that you are not.