This is a tricky one, and I may be painting myself into a corner in which case please feel free to tell me so in an answer but please also provide advice on how to get out whilst disturbing as little paint as possible!
I'm 5 sessions into a new game I've never played before and I've started fleshing out my character's background. I love detail so I'm attempting to tie it all into her class, her stats, her race, everything but I'm new to the game and I don't want to learn too much about the in game universe that will ruin surprises / locations / plot points / trivia that will likely be revealed in game (or in games to come).
For me, learning about the in game universe organically (as opposed to reading about it outside of the game) is one of the huge aspects of my enjoyments, and I don't want to spoil that.
How can I tie my character's background into a game I know little about?
I've deliberately left out the game details as I think advice could be system agnostic, and I've left out specifics of the detail I've allowed myself to learn out-of-game so far as I feel answers that give the minimum possible would be of more help to more people (who can then make their own concessions).
However, if it aids your answer: I am playing DnD5e, I've allowed myself a map of Faerün (although I am not looking up any of the places named on the map) I'm trying to tie in the loss of my orc father in a war (what war? where? I've selected a place but can I really make up my own war?) and I'm claiming I learn Dwarven and Elvish on route to find him (as a result of a chance encounter with some Elves at Location X, but what if there is no way Elves could make their way to Location X, in fact Location X's one defining characteristic is that it has never had Elves in it ever!).
Best Answer
Work with your GM
The key thing is to work with your GM to determine how you should be linked to certain things and how much you and your character should know. This can be an ongoing conversation and your background can change and grow in depth as the story develops. If you like you can think of those additions to your background story as akin to a literary flashback.
Your character likely knows a bit of setting lore and you should too.
You mentioned you want to avoid spoilers, and to a certain extent that is a good thing, but remember that in most scenarios your character will know a fair bit of the lore of their world and will likely know their own personal history.
There are of course exceptions to that. A pseudo-medieval peasant may actually know very little of what is going on 20 miles away and what they do know may be exaggerated. But in most games the PCs are assumed to be more competent than that and are generally in some way special. Also, even an illiterate psuedo-medieval peasant that has never traveled will know his own hometown.
In short, as long as you aren't delving into spoilers about your specific campaign, a certain amount of background knowledge is likely to be expected and helpful. Again, you can work with your GM on the details.
Have your character be a recent arrival.
Again work with your GM, but more specifically, one of the easiest ways to flesh out a background without worrying about spoilers is to have your character be a recent arrival to the region where most of the action will take place. Then you can detail all kinds of adventures for your character before the start of the game without worrying about interfering with the GM's plans because they all happened over there. The GM might then decide to have some of those loose ends follow you, but that will be the GMs call. The GM is equally free to leave them all as the way your character discusses his own history.