The following meal plans are for anyone who is underweight and looking to gain weight on a budget. They are based on simple foods that should be easy to find in your local supermarket in most countries. They can also be used by people who would like to build muscle, if used in combination with an appropriate strength training program. Days 1-5 provide approximately 3000 calories and would be expected to result in weight gain of 1-2lbs (0.5-1kg) per week, depending on gender, body size, and activity level.
Days 4 and 5 are designed for people who would like to cook food in batches for the week to save time. That said, variety is key to a healthy diet, so try to vary your diet as much as possible including different fruit and vegetables with the meals.