Here's the thing. While the plot is really important, and will be what people are along for the ride for, characters matter a lot. A character can make or break a story. If you have a really interesting plot, but a really unlikeable, or boring main character, people might lose interest in the plot. The main character is our entry-point into the story; if they're not relatable or interesting in some way, there's no way to get into the story.
You don't need to give us all the details on a character; we don't, as you say, need to know how someone likes their eggs in the morning. We need personality, not big info-dumps on backstory. To second @joannekwan's use of Mad Max as an example; we don't get much in the way of details on Furiosa. We know the very basic premise of how she ended up where she is when the movie starts, and we know what she is aiming for, but that's all the spoken information we get; everything else we learn about her is evident in her actions, her decisions and the way she relates to other characters.
Right, more general tips.
While I can't help you with creating ideas, here's how I go from vauge idea to something that can be turned into a comic.
1.) I take the initial idea ("Girl has adventures in space - also, robots!") and poke at it until I get some sense of what I want to do with it, and why. Is there a theme to this story? What am I trying to say? What are my reasons for going with this particular story?
2.) Once I've decided where I'm going and what I want to tell the reader ("I want to make a scifi-world where none of the stories revolve around white, cisgendered straight men"/"I want to tell scifi-stories where the future is bright and hopeful."), I turn to crafting characters. Sometimes, these first two happen simultaneously - I can't really divorce character from story. I scribble character designs, try out personality traits, cobble together relationships between characters, work on things like what their goals are, what things they would do to get there, and that they definitely wouldn't, etc., etc.
2.b) A subset of 2.) - I work on the world in which the story takes place. If it takes place on earth, in modern day, this step is pretty simple, and consists mostly of deciding what the framework of the story is. If it takes place somewhere else, this step can take a long time and a lot of work - but I like building worlds, so I enjoy it.
The important things are to firstly focus on the stuff that matters to your story. If it's not directly related to your story, it's not important; you can work on it in your spare time if you want, but it's not necessary. Secondly, it's a good idea to give the world a sense of existing beyond your characters. It was here before your characters, and probably got along well without them. Not everything in the world needs to center on your characters.
3.) Try to turn this big barrel of stuff into an actual script for a comic. Break it down into manageable chunks, whether that be chapters or scenes, and arrange them in some sort of readable order, keeping the dramaturgical arc in mind.
4.) Draw.
5.) Worry about the dialogue. Dialogue is hard, at least for me. I always want to say more than I can rightly fit into a speechbubble without it looking cramped, so I work really, really hard at saying what I want to say in as few words as possible - and as simply as possible. Keep some things in mind; the way friends speak to each other is different than the way a superior and a subordinate speak to each other, and there is no set model for that speech. Some people are super-polite to their superiors - others are really not. Some people tease their friends a lot, some people don't.
And we speak differently to different people. To use Grassblades as an example - the way Masahiro speaks to Akane is different from the way he speaks to the nun in the first chapter, which is different to how he speaks to people who will turn up in chapter two, and so on.
The best place to start might be with yourself. How do you speak to people? Go with that first, and then you can tweak it later.