At 2years, your baby should be able to eat most adult foods e.r rice, beans, semo, bread. So ensure he eats a balanced diet, give fish, meat, milk, vegetables and fruits regularly. It is preferable to use milk appropriate for his age (e.g. peak 1,2,3 or any other milk specially made for toddlers). If he is a picky eater, you might need to find innovative ways to combine and present his meals. Also, be patient with him as you try to improve his weight.