This question also relates to this one How Do You Access Your Storage Safe In The Storm Shield?. The 50 extra slots you got from the deluxe edition are not actually for storing crafted items or consumable items, it is used to store schematics and stuff. In order to keep your bag empty, you will need to open up the menu for the bag and start recycling items. This will clear some space and give you materials for the stuff that you get rid of.
For the moment you just need to be very smart with managing your inventory space. I created a guide for this as I have found some good ways to keep on top of it all. 7 Tips For Managing Inventory in Fortnite.