Gainers are an easy option of getting in the extra calories along with the rest of your daily meals, just watch the sugar content on some of the products, you want to gain muscle weight not fat weight!.

I would recommend chemical nutritions Pro Mass...superior ingredients than most.

http://www.affordablesupplements.co....asp?prodid=122

Not how much to consume per week, ..you need to do it per day. To work it out......Your weight in stone x14=? x15or17=daily calories. This would be a good starting point to gain and increase gradually.

Try Ratio as follows.
Protein 35%
Carbs 50%
Fats 15%

Six-seven meals a day spaced out every 2.5-3 hours with good breakfast and post workout nutrition are of up most when gaining.

Idea for Foods to consume;

Carbs.
Brown Rice
Brown Pasta
Oats
Wholemeal Pitta
Wholemeal Bread
Sweet Potato
Fruit
Veg

Protein.
Eggs
Lean Steak
Shark
Chicken
Turkey
Salmon
Tuna
Prawns
Cottage Cheese
Peanut Butter
Yoghurt
Skim Milk

Fats.
Walnuts Cashews
Oil Blends
Flax

Hope that helps.