The Basics are the things that you should have in each pack you make. So when you are putting together any bag you will start with the basics. The basics don't change and however many bags you have you will have that many redundant items.
Bug Out in Vehicle gear is gear that you would take with you if you can take your car. If you have enough room to take heavier and items too bulky to carry, extra gear, extra water, or a bigger tent. Your Bug Out Vehicle bag is what you should make first as it is more likely than bugging out on foot and more severe then bugging in. And as you will keep this bag at home, it can still be used to bug in.
Get Homegear is for when you need to get home or are stuck at work. In some cases you may need to walk or take an improvised method home and you what you wear to work may be fine for the office but not for getting home. This is gear that will stay in your car. As it is more likely than bugging out on foot or bugging in and more severe then staying home it is the second bag you should build.
Bug In gear are the things you will use if you need to shelter in place. Many of these things you won't be able to take with you if you need to leave. Even though bugging in is less severe than bugging out on foot, it is much more likely so it should be your third bag you build.
Bug Out on Foot geat is what you will take if you can only bring what you can carry. This is the worst case scenario bag. Once you start to get a feel for your gear and how to use it, you can modify one of your Bug Out Vehicle bags to be you Bug Out On Foot bag, depending on the room you have. As it would be assumed you would take you Bug Out On Foot bag with you if you did take your car, you can now buy a few extra pieces that are specific to backpacking.