1. Main - a few core items that are used in any situation and for very short-term (from a few minutes to a few days);
2. Secondary - add items depending on the geography where I will travel, similar duration;
3. Outer – longer term items, over a few days because help may take a while to arrive.

Perhaps another way to look at it may be:

1. PRIMARY: those items that assist your 3 primary concerns and which can be legally carried anywhere as "carry on" bag. This would obviously be a very small amount of gear to be able to carry on any aircraft, to any destination, legally. It would be a very basic EDC type of kit.

2. SECONDARY: that gear which meets your primary needs and can legally be checked in baggage anywhere that you fly to and anywhere that you land.

3. OUTER: that gear which meets your 3 basic needs but isn't legal in every destination. You get that gear that is legal, locally, and leave it behind if it is illegal at your next destination.

These are just my opinions and worth every penny you've paid for it. Also note that I haven't flown overseas since 1999. There have been major changes everywhere since then.