First see if theres any rules restrictions for what ever games you intend to play?
Then i would tell you to go and get behind as many scopes as you can and see what you like.
Im not shooting F class or out to 1000 , I get out to 600 yards couple times a year.
i dont like the reticles that are cluttered with graphs, Xmas tree reticles . Then be sure where your reticle subtension equals out if you want to use your reticle for hold overs with out remembering a bunch of stuff. Applies to 2nd focal plane scopes
For example a mil or moa reticle will often be at the highest magnification for scopes under 24x meaning if you want your reticle hash marks to be spaced equal to moa or mil it has to be on 24x ....my sightron SEIII is 8x32 and scope subtension for moa is on 24x
Then the next step: how much are you looking to spend.
I think if you spend at least the same on optics as you did on the rifle you will start off pretty well.
I only know a handful of people active in F class and 1000 yard shooting . All run nightforce, March and one has a SB
All are dumb big 34mm tubes 56mm lens and IIRC are 50 magnification ? Now that my eyes are aging to the point where shooting Iron sighted rifles is no longer fun for matches im getting drawn into scoped events. For the money the sightron is nice less than $1000 on sale. Although i really liked the night force comp model i tried few summers ago. The March scopes are really nice but another big step up in price.
I was blown away with the clarity of 50x and the 1/16 moa dot