Any survival kit you make is better than a store bought one. You care about your a**, the store cares about your $$$. I use a Doug Ritter PSK as a base and add to it. It is the most honest kit out there. He tells you it is an incomplete kit and gives suggestions of items you may want to add. Try to find that info on any of those "complete" kits!
SpeedHook (for fishing) and Thompson survival snares are something you may want to also look into. SpeedHook is kind of like a snare for fishing.
"How To Build The Perfect Survival Kit" by John D. McCann is a great book. I knew much of the info but it really helped me organize my kits.
"98.6 Degrees" by Cody Lundin is a good book too but get the above first. This book is 1/2 survival and 1/2 kit book. If you do make your kit like Cody's it will weigh around 2 pounds. I made two and ended up breaking them down for other kits. A two pound kit is fine if that is all you carry, but if carring a full hiking load then a 2 pound kit is a bit heavy.
The #1 rule of making a survival kit is DO NOT PACK ANYTHING YOU HAVE NOT TESTED! Condom as water carrier? Doesn't work for me. Mag block? Doesn't work for me. Cotton balls? Doesn't work for me. I use Zip-lock bags, Firesteels, and cotton/wax "earplugs". Also found out that a brand of lighter died while in storage even though it still had fuel
This is why I like to make two kits, one for training and one packed ready for emergencies.