My preferred tire kit is the Rema brand kits. The TT-02 has the best mix of patches for most situations. The small round ones are good for single punctures from road debris. The larger oblong ones can handle small cuts and “snake bites” from rim impacts. These should be bought from your local shop.
My approach has been to install another tube when a flat occurs. I like being able to take my time and repair the leak in camp at the end of day. Multiple flat days require a more pragmatic approach and I deal with them as they arise. I carry 2 spare tubes on any tour where I have my full touring kit.
I make a double kit for several reasons. The most obvious reason is to have more of both size patches. The less obvious reason is to have 2 tubes of glue. One tube is used first and the other is only opened if absolutely required. The moment you realize that the glue tube has dried up is not a moment I wish to experience. Always having a second “new” tube is cheap insurance.
Over the past decades the glue squeeze tubes have improved. They used to be made of a lead based material (I think) but now they don’t crack as easily and I have not had one dry out or leak in a long time. The patches have not changed much as far as I can tell, that is fine with me they are and always have been fantastic. I am curious if tubeless tires will become the norm in my lifetime.
I also add a Schreader to Presta adapter in the patch kit. Each of my wheels already have them as valve stem caps but they are small and easy to lose. The box the kit comes in opens easily. A ponytail elastic works great to keep it closed (also fantastic for color coding mini/micro/typeC USB cables) but I am out of them after sorting all the USB cables : )