Like most broad ideas backed up with books and references in game to form a core.
Then I spend time exploring facegen untill some mixture of looks and facial traits come out.
After which is a backstory and idea of how much they would or would not do or items, spells and skills they would not touch on.
Then comes personality traits, often brought up in the first few hours of gameplay, followed by their interactions with Npc's out in the game world.
So sometimes I get very specific characters that take me into weird or beautiful roles.
Othertimes I end up with a more general explorer that is only slightly more fleshed out to just bash heads, and see sights.
My first couple characters were just videogame stuff. Didn't put much thought into what I wanted them to be, so the 2nd one especially wound up becoming this jack-of-all trades. That would have been Renee Gade the first. She was trying to do every quest that was thrown to her (except the Main Quest). Her game got out of control. Leveling was going really fast, I hated the way all these creatures started popping up out of nowhere (where were they all before?) One day I stopped playing Renee Gade I, put Oblivion aside for almost 4 months.
Same here, though with my latest dunmer Osmundas Hlaalu being a Jack'o trades is pretty fun.
I think if you just mostly focus on majors with such a build it makes the role interesting to play.
As yes he can cast spells but not many, he can use magic items but not make any.
He can bash heads but is limited to rushing in and out quickly and only usefull with a blade no ranged attacks at all, he can sneak but rarely uses sneak attacks.
Which makes him powerful but tricksy, and has given me a load of fun to use.