What I usually do is a bare bones approach.
This means that I leave the background story and tale of a character relatively ambigious and let their personality form out toward a theme that I want to portray (though that can also change).
FYI character background and story aren’t for others, its for yourself.
I am currently in the process of actually creating a new goblin hunter character with that approach. Right now, their background story is not really important, but I want to portray a gritty gunslinger character with a very practical approach to life and things.
Due to my binging of wh40k lately, I also wanted him to have a bolter-esque semi-auto firearm, and a very orky/imperial guardsman look. I have been very successful with this so far: Further, since we are talking of a hunter class, pets come to mind but I opted for him to have darkhounds instead of mechanical pets, because it’d make sense for a traveling person to have pets that are small enough to fit/travel alongside him wherever he goes, but also fierce enough to protect him- Which, darkhounds certainly are. They are also replacable for a non-caring individual, do thats great. Further, I get to tap into endless reservoirs of pitbull memes.
I’m unsure if this comes across in this post but I think a lot about practicality in terms of both RP feasibility and IC realism. Things that a lot of other roleplayers may not even think of, and my character building branches out a lot into logical assumptions and suspensions of disbelief.
To give an example, there’s 0 point to make a sniper RP character because its anti-rp interaction (since those being your target have no real way to interact back at you) and has a very niche field of RP you can play around and leans extremely heavily on player permission, much like assasin RP does.
So what i do instead is design a character for mid-to-close range rp, because thats where most of the rp in combat happens.
At the same time, I also give a lot of thought to the interactiveness of my characters- and while this does absolutely come down to your own enthusiasm, it is very hard to interact with others if you have decided your character doesn’t speak a lot or is very anti-social.
And this process grows organically as you test out what works and what doesn’t, until you got a solid character. Also, recognise yourself! Distancing yourself from your characters is a good thing to do, but also recognizing what things you like is ok- And inserting them (hopefully) in tasteful ways.
My quirk for example is humour and wittiness, and almost all of my characters have moments where they utilize that- some more than itters, and not always tastefully either. I’m not perfect, but I try.
My tldr is essentially: Your character doesn’t need to be, or perhaps SHOULDN’T be ready when you start to Rp with them. Just have a general idea of what you want, a general idea of the aesthetics you like, and a general idea of what themes you want to emphasize in your character. Then, you let them grow.
What I have found to be really helpful for myself is describing my character in pictures, instead of words. That somehow seems to make me able to make more thorough and multi-dimensional characters very effortlessly rather than forcing myself to write about their quirks.