Lunch Box

Hi Kyouko, 

You remind me of one of my favourite Japanese dishes -- Chawanmushi and Chuka Hotate sushi!

I would like to share why I have changed certain parts of your writing.

(1) I presume that you are referring to a regular and weekly routine of preparing meals for your son from Monday to Saturday. In this case, you can add the letter "s" to indicate this recurring act. 

(2) We can use "batter" to refer to a beaten mixture of flour and eggs with other things such as water and/or milk. We use batter for preparing deep-fried dishes. 

(3) We use "coat" to refer to covering something with a layer. In this case, you are covering the batter with a layer of breadcrumbs. 

(4) There is a difference between "fats" and "fat". We use "fats" to refer to one of the macronutrients found in food. We use "fat" to refer to someone with excess flesh, or an oily substance found in the bodies of living things.

Example: 

He is a fat boy. (obese, with excess flesh) / Polar bears have a thick layer of fat to keep themselves warm. (thick layer of oily substance) / Cakes, cookies and snacks are high in fats. (A type of macronutrient)

(5) You may wish to use the word "economical" to refer to something that does not cost much money.

Hope this helps.
Cheers

Lunch Box

While cooking, I try to organize a box with
three major nutrients, protein, fat and
carbohydrate.

Although I try to make a lunch box at a low cost , it is still hard for me.
To make a lunch box at a low cost means
I need to learn how to make variety of food

I am getting used to make a lunch box however I sometimes over slept in the morning then I ask my son to go to a cafeteria for lunch.

Corrections: 

I make a lunch box for my son between Monday and Saturday in the early morning starting at five thirty.Actually I need to do preparation the night before. 

For example, if I make Tonkatsu in the morning, I season the meat with salt and pepper then put it into the egg solution after coating it in flour, finally I roll it into bread crumbs which is my preparation for cooking fast in the morning. 

While cooking, I try to organise a box with three major nutrients, protein, fat and carbohydrates. 

Although I try to make a lunch box at low cost, it is still hard for me. 

To make a lunch box at a low cost means I need to learn how to make a variety of food. 

I am getting used to making a lunch box, however I sometimes over sleep in the morning then I ask my son to go to the cafeteria for lunch.