Singing coach would be the best answer. But outside of that I'd say the first step would be to train your ear. Pitch is more important than the quality of your voice. Plenty of singers get by with unconventional voices because they can sing in tune. And even someone with the most beautiful sounding voice will sound terrible if their pitch is bad. Developing a better sense of pitch is possible, even on your own over time. Look up ear training voice exercises.
Plenty of singers get by with unconventional voices because they can sing in tune.
That's a damn fact. Dave Mustaine has an absolutely awful singing voice (and an awful attitude but that's a different story) but he just went out there and went wild with it and became one of the most recognizable voices in classic metal. Recognizable largely because it's awful but he manages to spin it into something people want to hear. Nobody else sounds like him and he made a living off that.
I'd argue the same for Bon Scott and Brian Johnson of AC/DC. I'm not sure they could have made it in any other genre, but they did damn well for themselves playing good old rock and roll. It's about matching a style to your voice and then having the confidence to go out there and blaze a new trail. But I suppose that's the same for any music.