For your home base, your best option is to get a large, pre-prepared one, since they're designed to not be moved around and so are often very thoroughly stocked and cover a broad range of injury. Here in Australia, St John's Ambulance Service offer many nice pre-made kits, but most camping stores have them, too. They may seem expensive, but trust me when I say it's worth having one.
I won't go into too much detail on the full-size medkits, as the pre-made ones are often best, but what about the medkit that you carry with you in your 72 hour bag? Often the travel kits you can buy just don't cover things thoroughly enough.
If you live in America, then you're lucky enough to be able to order one of the only pre-made kits that is ideal. It's called the IFAK and it's made by The Skinny Medic, who has a fantastic YouTube channel covering first aid training. It also comes in a very cool "tear away" pack design so you can have it securely attached to your bag, but also have the ability to quickly tear it off and make use of it in a crisis.
If you don't live in the USA, then you can replicate this medkit yourself. Here's a video outlining what's in it:
One of the most important items in there which I'd like to hilight is the QuikClot. If you suffer a particularly nasty wound - say you're mugged and get a knife wound such as a stab or deep cut, that can lead to severe, traumatic bleeding, and your only option is to get to a hospital. Depending on where the wound site is, you can bleed out VERY quickly, leading to loss of conciousness, which means you can't get help. If you tuck a QuikClot sponge tightly into the wound, however, it absorbs all of the blood and forces it to quickly clot, stopping the bleeding and giving you the valuable time to get medical help. Even if it's long enough to be able to call emergency services and last the trip to the hospital.
I know it's scary and seems a bit crazy to think about scenarios like that, but I have personally been attacked by someone wielding a knife before, and it is, quite honestly, one of the most terrifying ordeals of my life. I still have a fairly nasty scar on my arm as a reminder of what people are willing to do to you if they're desperate enough. QuikClot goes for about $25 per sponge, but realistically, you should only need one in your pack. It's worth it. Grab it.
Another thing I would probably add to the above kit is one of the Israeli Bandages mentioned in an earlier post. They're pretty amazing, and you can check out the video about them by clicking here.
That's all for now! See you again next time!