For redirects I like to create a rule to direct versioned sites (like documentation) to either "latest" or the version relevant to me. I also like to redirect sites to a more user friendly version when applicable (like reddit.com => old.reddit.com).
If a site leaves me disgruntled when I visit it, I block it. If I find it too useful to block entirely (reddit) I lower it. I apply the inverse to sites I enjoy.
I find there are certain sites that have built-in search that sucks. One such example is Dockerhub. In that case, when I want to search for a container on Dockerhub, it may be tempting to use the built-in !dh, but that is no good. Instead I favor the "snap" search: @dh, which will just add "site:hub.docker.com" to you query. This will give much better results than !dh. This can also be combined with the "I'm feeling lucky" bang (!), so you can search for something like "nats @dh !" and end up on the Dockerhub page for NATS - without ever even seeing Kagi if you do it from your URL bar. I do this pattern all the time, usually with Dockerhub and GitHub.
You'll find with the above pattern that you'll start to want to apply this to sites that aren't natively supported as bangs. One such site for me has been Ollama. I added a !ollama to be able to search for models directly. It's also nice because just searching "!ollama" will bring me right to the homepage too, which is useful when I want to check to see if I'm on the latest version.
You'll also find there are subjects where you tend to prefer a small set of sources. Maybe it's some software or tool, or some hobby or something, where you prefer official documentation, maybe some known personal sites you trust, a reddit community, something like that. That's where custom lenses comes in. I personally have a lens for the operating system I use (GNU Guix) (as well as a !p bang to search for packages) which includes official documentation, mailing list archives, IRC archives, things like that. I'm sure there are probably similar subjects in your world that you would enjoy having a more focused search for :)
As for the Kagi Assistant, I pretty much have just wired up an Assistant to use my Guix lens as a search source. That is pretty nice, because I can just ask it general questions like "how do I install nginx?" and get focused and relevant answers, instead of having it go off on how to install it on irrelevant distros.