My meal plan atm, helped me gained a shed load of weight! idk if it will work for you but give it a go!
Breakfast: 400g porridge, 30g whey protein
Snack, 100g penut butter sandwich, pint of milk
Lunch, tuna salad/sandwich about 200g of tuna + vegies
Gym (VERY important part of weight gain, otherwise you just go from thin to fat)
30g whey protein
Dinner, anything thats very high in carbs + protein eg chicken, fish, red meat etc
Snack, 100g peanut butter sandwich pint of milk.