I think concentrating on improving social skills and learning to dress better are important. Regarding social skills, if you suffer from social anxiety, CBT, mindfulness and antidepressants work well. Apart from that, I don't really know, as my social skills improved without a great deal of effort, but good self help advice is probably the way to go. I also don't know a great deal about men's fashion, but googling "how to dress for overweight men" brings up lots of results. A word of caution though - after getting internet fashion advice check how things look with a friend!

I think losing weight is also good idea, but you may not be able to lose it sustainably, so doing other things as well is important. Recently, I've wanted to look better. I am going to try to lose weight (I don't have a great deal to lose, but I'd look better if I dropped a few kilos), but the first thing I did was buy some new clothes and get a new haircut.