Gains are made in the kitchen. You need to figure your diet out first. Junk food doesn't really matter- you need energy and calories give you energy. You will gain more fat if you eat "dirty," though.
Like SYN said- push, pull, legs. On push days, do chest and tri work. On pull days, do back and bi work. Start with major muscle groups first- bench press before you do skull crushers, do rows and lats before you do curls, do squats or deads before you do any auxiliary work like calves. Cardio should be done in small amounts, especially if you want to gain size. Go for interval training as this gets you the most benefit in the least amount of time- sprint for 30 seconds, speed walk for a minute, repeat up to 30 minutes.
Make sure you eat a lot of protein- if you do decide to use supplements, after working out would be a great time to drink a protein shake. Eat lean meats- chicken, fish, etc. Don't forget to eat veggies and fruits, or at least take a multi. Get calcium in your diet and don't be afraid of fats. Good fats come from low fat cheese, milk and yogurt or you can take fish oil pills- but you'll likely burp up fish taste from those. Yuck!
If you don't have a lot of gym experience, it might be in your best interest to go to the gym and get one or two sessions with a personal trainer so they can show you the correct form for each exercise- it does you no good if you use poor form and hurt yourself. For strength, I did 5 reps for 5 sets with HIGH weight. It should be high enough weight that you struggle on your last rep, but low enough so you can still finish with good form.