What he said. Squat, dead lift, press/bench and eat healthy like a horse. Also use your low weight as an advantage in terms of pull ups and dips - get good at them now while you're lighter, even though you're not going to be too strong at first.
I don't think I've found a harder exercise to improve than pull ups, and I sit around 190 lb and I can squat, dead lift and press reasonably well (nothing special, of course) for where I'm at (double bw squat, double and half bw dead, about 85% bw standing press). My best is 6 pull ups.