How often a person or family grocery shops is different for everyone. Some people shop once every week. Others only shop once a month. You will have to come up with a method that works for you.
Some people shop when they get paid. This means that they shop once a week, twice a month, or only once a month. Shopping when you get paid helps you to have enough money for groceries. But if you don't plan well, you could run out of food before you get paid again.
People need to do more planning when they only shop once a month. You need to make sure you have enough food for a whole month. There are ways to do this so you aren't eating macaroni and cheese at the end of the month.
Sit down and plan out most of the meals for a whole month. Make sure you know what you are going to eat for breakfast, lunch, and dinner. If you know you eat dinner out once a week, you won't have to plan meals for those times. Don't forget to figure in snack foods, too, if you eat those.
This sounds like a lot of work. But it will make the job of shopping for all this food much easier. You may still need to go to the store between shopping trips for items like fresh fruit. You can buy extra milk and freeze it. Just be sure to take about a cup of milk out of the container before you do.