A personal first aid kit is kind of personal. Everybody's should be a little different and even change a little from time to time. You really need to think about this.
1. Everybody goes to different places, so there are different risks, so the first aid kits are different. Somebody in Alaska might need to do first aid for a brown bear mauling. The guy in Florida doesn't need that. The person in Arizona might need to prepare for snakebite, and the one in Alaska doesn't need that. The guy climbing Denali doesn't need most of that, but he does need things specific for cold, burns, and blisters. Go to a third-world country like Nepal, and you better be able to self-administer treatment for waterborne illnesses. Some people are on trails and have one set of risks. Others are off trails and have a deeper set of risks.
2. Everybody has a different concept of what a first aid kit should contain. Some people load it up with chapstick, sun cream, water treatment, and stuff, and those really aren't for first aid. Some want their first aid kit to contain only enough stuff to keep a victim alive, and very little more. Some people don't even put bandaids in their kit, because they know that a wound small enough to be covered by a bandaid probably isn't large enough to kill you. Of course, if the wound gets severely infected, the story changes. Some people know that they get ankle sprains, so they better have a good elastic wrap to bind that up.
3. Some backpackers go out for only two or three days, so they do not pack long-term remedies. They figure that they will be back to civilization soon to get some care there. The backpacker who is out solo for a week or two at a time needs to think about long-term remedies. Antibacterial ointments come to mind.
4. One of the standard backpacker injuries happens when the backpacker is attempting to step over a tree across the trail, and he manages to impale his leg on a jagged branch sticking out of the trunk. I've never done that, but I've seen others do it. How would you treat that? If the wound is deep, there is a risk of bad infection.
A friend of mine was going out solo into the Sierra Nevada Range for more than one week. He was postholing through some late snow, punched through into a hole, and tore up his leg with a deep gash. Once he got the bleeding stopped (you did bring some sterile gauze, didn't you?) and the wound cleaned out with drinking water, he did temporary suturing with his ordinary needle and thread. By the time he got to a doctor over one week later, the doctor checked his work and approved. Many backpackers could not have done that.
Personally, I carry only about one yard of duct tape, and it is more for gear repair than for first aid. I've found some medical tape and some athletic tape that I really like. Pills can be good, and they don't weigh much.
I was trekking in Nepal, and I was up around 14,000 feet when I sustained a painful muscle injury in my diaphragm. Fortunately, I had some prescription-strength painkillers, and that got me through the next day or two.