Maybe try reading some books about networking, making friends and widening your circle might help.  Joining some clubs which have people with similar interests should help broaden your circles... do you have some cheaper hobbies/interests that you could connect with people over.

I read a while ago on a forum somewhere, that the most important thing they have tried to do in their post JW life is to engage.  As a JW we are taught from an early age to observe life, and not fully participate.  I dont think it matters whether you celebrate the holidays/birthdays or not, it really is up to you but maybe make it a goal to find social activities you do enjoy and make an effort to not simply 'be there' but to engage and be absorbed in the experience.

Wish you all the best