I install AUR packages “by hand” and maybe ran into this twice, where I had to install AUR packages to install an AUR package. That’s over a course of many years. It’s not a common occurrence.
What packages are you having trouble with?
Also, very important to know, using -S in pacman is called a partial update and it is not supported. That doesn’t mean you can’t do it or it doesn’t work, just best to avoid it. Always use -Syu. The full nuanced explanation can be found here wiki.archlinux.org/title/System_maintenance#Parti…
I wouldn’t disable sudo. This isn’t windows where all users are admins by default. It’s an important security feature to prevent unauthorized things from happening.
When you run makepkg to create a package from a PKGBUILD file, you can use the -s switch to automatically resolve dependencies from the repositories.