Buying an Xbox Card is easy and can be purchased either from a Microsoft Store or from a grocery or departmental store. There are multiple online platforms that give you the facility to buy gift cards from their platforms. All you need to do is:
Apart from this, you can also visit a store where they offer you the option to buy gift cards. You just need to ask the cashier for the card, pay him for the same, and give the card to your friend or a family member.