This is driving me mad.I do not know which is best format & how to show all category in home page.
Please follow the below steps to show all categories in Home page.
Login to Magento admin panel and go to Content->Pages
Select Edit option for Home Page
Click Content from left side navigation section
Remove all the unnecessary section from the content area and click widget from the editor
Select the widget type as ‘Catalog Products List’ and enter the basic information. In the bottom you can see the conditions to add. Select the option ‘Category’ and select the category you want to display in home page and click “Insert Widget” button. Similarly you can add all other categories you want to add.
Save the page and clear the cache.