I think a separate Category table will be easier. You can use a single table, but there are several additional columns you need to add and end up with an IF column that returns a category name only the first time that a category shows up in your table. Then you can filter a category list where the IF columns value is not empty. Then once you are viewing a category, you would need a ‘Show New Screen’ action to view the items.
It is not a goal of Glide’s to allows ads to be placed on apps. You can if you want, but you might have to build some the functionality yourself, and your options might be limited. I don’t think it’s straight forward or easily possible to add something such as Google Ads to your app.