As for me, I'm 6'0" 155 lbs, 27 years old. I want to gain weight. I was even thinner in high school, but worked up to 180 lbs while in college. I continued to work out for about a year after I graduated, but when I went back to get my degree in physics, I got out of my routine and turned into Sheldon from The Big Bang Theory.
Now I'm finally out of school, working full-time with a regular schedule, and can get back into a routine. Unfortunately, I now live in NYC and all the gyms around me are really shitty, and I have limited space in my apartment.
I just got an adjustable bench and some adjustable dumbbells (5 to 45 lbs in 5 lbs increments). I also have one of those iron gym pull-up bars that goes into a doorframe. That's about the best I can do with the space I have. Fortunately, because I'm so weak right now, the dumbbells should last me for at least six months before I need more weight.
I plan on doing a really basic three-day split, probably doing back/biceps one day, chest/triceps another day, and legs/shoulders the third day. I walk about two miles a day so I'm not too worried about cardio, but I will probably start running and/or biking when the weather gets warmer.
I would like to get to a lean 170 lbs by the middle of June. That's about 3 lbs/month which ma be a little optimistic, but I'm hoping for muscle memory to help me out. If I'm a lean 175 lbs by this time next year, I'll be really happy.
My primary motivation is that I'm going bald and I would like to avoid looking like someone who's gone through a couple rounds of chemo.