Yeah, ditto with prince Albert.
Weight gainers are only good if you have a truly hyperactive metabolism. Chances are you don't, and you'll just pack on fat mass. Sure, you will 'gain weight', but it won't be lean weight.
Just try and eat more good food, or perhaps start a habit of taking a few tablespoonfuls of oil every day (around 90-100 calories per spoonful), such as flax, fish oil, rape oil, or olive oil if you can't find the other types or want to cut down on expenses.