first of all thank you so much! my main recommendation for writing dialogue sounds kind of silly, but genuinely talking to people in real life helps so much. all kinds of people. listening to people talk, observing different vocal patterns, conversation trajectory etc., has helped me a lot. when i write dialogue (even outside of fic) i try my best not to worry about it sounding poetic or deep or even meaningful to the rest of the story (*******at first glance. i believe all dialogue should be purposeful) because most people just Talk like normal people. watching movies/tv and reading screenplays to study dialogue also helps a lot. the golden rule of writing that i live by is showing and not telling. real life conversations are made up of subtext. things that aren't said are just as important as things that Are said. generally speaking, real life conversations are not polished. most people don't say exactly what they're thinking, the 'right' words, people say ummm and uhhhh and they use filler words and they take pauses. they stutter and they forget words and they drag syllables out. people go on tangents and sometimes people talk just to talk. so i find the meaning within that. i think a lot of people get caught up in trying to sound poetic and unrealistically flowery, but the more natural the better (at least for my tastes) seriously, less is more! oftentimes even one single word can be so much more meaningful/give you much more insight into a character's psyche and world than a large monologue or speech ever will. sometimes large monologues and speeches are needed, but most real conversations are made up of cutoff sentences, people speaking over each other, and nonverbal glances and cues. humans are imperfect!

each conversation should reveal something about your characters, and that can be something as simple as "he likes to make jokes" to something deeper like "he backs down from arguments easily" and by revealing something about your characters in dialogue, you make your characterization and narrative stronger. why does he back down from arguments easily? ---> because he hates confrontation. ---> why does he hate confrontation? ---> because he wants everyone to like him and he's scared of conflict. ---> why does he want everyone to like him? ---> and it keeps going. you know what i mean? LOL

in terms of unique voices, that goes beyond dialogue and more into characterization. personality plays a big role in how a person speaks, and so does objective/who they're talking to/what social setting they're in, even how and where they grew up, etc. if you know your characters well, making them distinctive from one another will be achievable because each person you're crafting is unique. really make sure you know each character's point of view, and the rest will come easily

tl;dr, be intentional but don't be afraid to get messy and funky with it. what i mean by that is, don't be afraid to make your characters sound human because they are. i hope this helps at least a little bit 😭