If your Target is to Get better Body then you should join gym or If your target is to just gain weight then no need to go gym.
I am Big Fan of Hrithik Roshan (actor) . Always wish to make body like him. :)
MY OWN EXPERIENCE
10 Month ago i have same Question. I did some research about body building fact and join gym.
when I Join Gym My weight is 58kg and Height is 6 feet, Within a 5 month of proper Diet and Workout i Got 70kg. I am pure vegetarian.
Here is my past and Present Picture.
Diet & Routine : Normally i finish my workout in 1.5 Hour.
I have Monday to Saturday simple But heavy weight Workout.Like One part in A day, Monday Chest, Tuesday Triceps, Wednesday Back, Thursday Biceps, Friday Shoulder, Saturday Legs, Alternate day Abs.
About Diet, I leave in PG so Sometimes i need to compromise in Food,
If you have your own kitchen so you can do far more better, I Am taking
7:00 Am Sprout Mung at morning/Banana
10:30 Am 500 ml Milk with whey protein(Past i taken Mass gainer)
1:00 Pm Lunch( whatever in Dining Hall :) )
4:30 Pm 500 ml Milk and few Biscuits
7:30 to 9:00 Pm Workout ( now i am doing workout at morning)
after workout Protein powder with water
9:30 Pm Dinner
12:00 Am Eat Banana or whatever i have to eat
Thats what i did, Always I am try To experiment with diet and workout,Some are work and are not.
Hope it will be useful for you, :)
Thank you