Hi, I live in Delhi and I travel a lot in north Indian states. I will share my experience with you regarding top snacks and street food which I eat a lot in India.
Samosa :- Its one of the most popular street food in India also very good in taste. It is made up with gram floor and potato, smashed spicy potato is filled inside triangle roll and usually served with spicy red and green chilli sauce. Its very easily available and pretty check in price like you can get 2 samosa in 20-30 Rupees or price depends on place where you eat.
Aloo tikki :- Aloo tikki is another most popular and common street food found in India. Its made of spicy smashed potato and cooked on plain tava with edible oil. Aloo tikki is usually served with sweet red and green chilli sauce with chopped onions. It is also very cheap in price 40-60 Rupees per plate or price depends on place where you eat.
Pani puri :- Pani puri is very tasty and demanded snack in all over India. Panni puri is a hollow crispy ball made of wheat flour, upon serving it is filled with spicy green liquid filling along with sweet sauce. It is most desired snack amongst women and kids.