OK, so here are what I typically would have for overnight trip to more.
Main back pack with:
1 set of clothing
1 set of cook kit
1L water bottle
Food bag (with food)
Then in the side bag and on the belt:
Stove and fuel
Emergency fire kit
Map & compass
Dump pouch (this item is missing from picture)
Depends on the season and weather, I also add extra clothing like wool sweater, wool under shirts and jackets, but this basically covers all I need for most of trip.
now, the part I would like to point out is that this set up contains several redundant items. The obvious are the blades, I have 4 knives and 1 axe packed. Puukko (main knife) on the belt, 1 SAK in side bag (the secondly knife), other SAK in FAK (for medical usage needs, keeping this as clean as possible at all the time) and one folding knife in fire kit. All these have primary usage but meant to back up each other. so all of them are packed in different locations. So if one goes missing, still have something.
Same idea goes to fire starters. one in fire kit, one in cook kit (main use). one in my pocket (oil lighter or matches for quick needs) and sometimes one more on knife. also fire starting aid are available in fire kit and many items from FAK, like hand sanitizer, disinfectant and cotton pads.
what about water? I have main container in back pack and small one in the side bag. Same thing with cook kit. main cook kit and canteen cup as a backup for boiling water.
shelter??? One I am wearing and one packed. poncho shelter is parted in 2 pieces. half is for rain poncho and other parts are packed in the back pack. the ground sheet could be used for covering as well and of cause emergency blanket is in the fire kit.
for emergency signaling, I have phone, whistle, mirror, flash lights, fire.
the only item i do not have back up is for the navigation and I am working on it, but have not found the solution I like. You might say, what about phone GPS for that? yes, it can be used but not very reliable because of battery life... so I am NOT counting on it.
So, all of my gears have back up and when I listed up like this, it sounds over doing. But think of it, I do not have any extra gear packed just for back up purpose. all of them are needed or I anyway do carry, it just those have the primary function and secondly function. Also most of the secondly functions each item has are still in the range of its intended use (some might be pushing a bit...), so still safe and sure to use.
Talking about safety, one thing I really would like to point out is that "Never take an item you have not tested yourself". Especially the one you made yourself or modified yourself, but also for the equipment(s) straight from the shop.
DIY and modified gears are clearly not trusted until proofed. But one from shop also should be tested before actual usage. so you know exactly how to operate, how it react to different conditions.
Fail of equipment might cause serious un-comfort or in some casemight harm your health. So, tested on your back yard (moderation test) till you are comfortable with it, and if possible, take it with you to short hike or day trip to test (field test) it again..