What's the best workout plan for a skinny guy?

I weighed 85 lbs. at 15 years old and now weigh 165 lbs. at 21. In that time I became and avid weight lifter, played H.S. football, college rugby and college football. I'm 5'8" 165 lbs. I did p90x and it helped me smash through some of my strength barriers, but what really helped was changing up my weight lifting routine. Try doing heavy squats and dead lifts and changing up the order you do exercises in. Changing the order, # of sets, # of reps and introducing new exercises helped me hit new gains. My diet consists of protein, carbs, and vegetables. However, When I'm looking to gain I take whey protein shakes and amino acid capsules. Also, make sure you're working hard to get those last 2-3 repetitions. Don't cut cardio. You're losing weight due to cutting water weight. Just keep your self hydrated...My main mass gaining excercises...Benchpress, Incline bench press, Squats, dead lifts, cleans, overhead press, heavy curls, Lat pulldowns, skull crushers...really it's just finding that combination your body reacts to...You know when you're working hard...Heck, you gained 12 pounds since January...that's a hell of an accomplishment, If that plan quits producing, switch it up. Big gains are caused by your body adapting to changes, but if you dont change it, your body becomes accustomed to it.