You won't be satisfied with a 10 pound gain. I've weighed 138 lbs since I was 15 years old until recently. I tried from 15 to 23 to gain weight, trying all products, supplements and mass gainers. I have an extremely high metabolism and I have Gluten and lactose intolerances, IBS and acid reflux, so I am also extremely Limited in what foods I can eat.
For the last 3 weeks I've been supplementing Herbalife24 Products along with Gaspari Nutrition Real Mass Probiotic series. I take in 1300-1800 calories from shakes a day. and 1000 about from food, I also consume Kombucha (probiotic tea) to help absorption and keep things moving along in my intestine. I take L glutmine before and after workouts with my shakes.
I drink a gallon of water a day or more, I just keep slamming water all the time, our body is over 90% water, so that should be make a lot of sense!
I consume about 400g of carbs or more a day, and 150g minimum of protein. On workout days i make sure I have my 2000 calories and 300g of carbs before the workout, and I take a preworkout with Arginine and creatine.
In 3 weeks i have gained 12 pounds! I am now 150 pounds, and i never even dreamed I could have weighed this much.. and I'm not satisfied. My goal is 180 by the end of this year. I'm an even harder gainer than YOU!!! So you can do this.
It's also about doing the right workouts.
I'm 6'2" at 150 pounds now. where i used to be 6'2" at 138 pounds just 3 weeks ago. You can look at my pictures to see. Eccentrics styled workouts have given me more size than I could've hoped for, and I didn't know what eccentrics were until a buddy showed me.
A lot of my routines are taken from Arnold's encyclopedia of body building

a 30 year old book my father has had, but I'm sure you can still buy it. "winning Bodybuilding: by Franco Columbo is another book I am taking my workouts from.
I do 5-10 minutes cardio, 10 minutes active stretching, 10 minutes of arm/shoulder warmups and regular stretches.
For workouts, I do 3 sets. For example my close leg-leg press I start out with 175 pounds first set of 12. then 225 2nd set at 8. Then 3rd set at 300 pounds at 6 times. Then I do a "burnout" where i do as many as I can at a lower rate until i can't do anymore at all. you ALWAYS want to hit failure.
My total workout time doesn't exceed 1 hour and 30 minutes.
I have a friend helping me with form and he's never seen anyone gain weight as fast as I have....when I've had a failed history of trying to gain weight.. and I even considered taking steriods.... Members on this website told me not to take roids and convinced me that I just need to eat more and train harder.
If I can do it all natural, you can do it too.... I still look skinny as all hell, but I'm 12 pounds more than I've ever been in my entire life and I love it.