>graphic novels so that i can read a self-contained story without having to scramble all over the place.
First things first, get rid of this mentality. You'll never really "get into" comics if you're afraid to actually read ongoings.
Beyond that, your fear is mostly unfounded. While crossovers do happen, pretty much every comic allows for you to read the same magazine without absolutely needing to read other shit to get the full picture. If you read from the start of a writer's run, you will 99% of the time be perfectly fine.
Personally, both The Killing Joke and Watchmen are AWFUL places to start reading comics. Terrible, terrible, fucking terrible. Watchmen is terrible to start because you're not going to remotely appreciate how unique its style is compared to other comics, past and present. Nor, I'm assuming, are you going to put much effort into consuming all of the extra bits: the more boring/less action-packed pages, the side stories, the back matter, etc.
On the other hand, The Killing Joke is not just overrated, but edgy as hell, in a cringeworthy way. You shouldn't go into comics thinking, "Wow, this edgelord shit is what people consider good, huh? I guess that's what I should be reading!" Otherwise, you'll seek out the lowest of the 00s' trash, and no one should suffer through that.
If you want Batman recs, see . If you want some of Moore's works that are both good for starters and not embarrassing to read, see , his America's Best Comics output (e.g. Tom Strong, Top 10, Promethea), and his run on Swamp Thing.