Training is going to be the best remedy. I started training in September at 119lbs, I now weigh 134lbs. All I've done is change my diet a bit(still not the best, but it's better then before) and add training.
Don't worry about weighting yourself too much, only once every 2-3 weeks to really see some results. From one skinny guy to another don't spend too much time worrying about what you're eating.
-Remove pop/coffee and try drinking more water/juice.
-Try eating something good like pasta over pizza.
I was thinking about picking up a protein supplement in the new year myself, but I'm going to be halving what it recommends. More interested in a little something extra to smooth recovery then just adding more bulk.