Focus on Nutrition! The key to gains is your diet especially if you're an ectomorph. When I first started a good regimen that worked for me was a 3 day split of combining your pulling movements and pushing movements. Mon=Back/Biceps - Tues=Off - Wed=Legs - Thurs=Off - Fri=Chest/Triceps/Shoulder - Sat/Sun=Off. You can integrate cardio on your days off but if weight gain is your goal with your body type you have to be careful of inhibiting your growth. Don't over do it on the exercises or repetitions just enough to break down the fibers (don't live in the gym) and get a good workout. Remember you don't grow in the gym so Rest is a very important factor as well. Goodluck
Hope this helps.....
P.S. Whey protein, Weight gainers are great but most of your caloric intake should be from whole foods.