For me the three main legs of a novel are character, story and language. Often , since I write speculative fiction, I'd add a fourth: setting. This can still be true for other types of fiction, too, but most true for fiction that uses world-building.
Some people start with a character. A character comes to them when they're out on a walk or in the shower and they want to write a story using that character. Some people start with plot. They have an idea for a story. Some do start with a setting and that setting is where their kernel for a novel comes from (1984 maybe). Consider To Kill A Mockingbird. I've never talked this over with Harper Lee but I can imagine her starting with a character (a young girl in a small town with a unique voice) or a plot (a story about a black man falsely accused of rape in a small, racist town) or setting (a small town that has many good people and good qualities but is racist and a situation exposes that and creates a tragedy).
When you're trying to get started, start with whatever kernel comes to you. NOW FOR THE IMPORTANT PART: you need to recognize that whatever you start with you will need the other elements to develop your story. If you start with an interesting character you need to be aware that he needs a story that will develop him in an interesting way and give him a sense of progress toward some goal or toward getting what he needs. If you have a plot that's about a journey or surviving an event you need the right characters for the specific journey. A girl from Kansas going to the OZ worked out pretty well for that particular story.
You have to do the work on this. You have to be aware that if you just try to write a character sketch your novel will likely die. If you have a plot but your characters are stick figures you move to make your plot work, your novel will not be read. Readers want characters they can identify with and care about. They won't keep reading if they don't have that.
My advice, fellow writers, pay attention to these aspects of fiction. Make them work together from the start and keep trying, as you move through your manuscript, to develop them. Your work will improve
Or so I think today.