With any rifle, you're going to have to buy a few different boxes and try and find out what shoots best in your rifle. Every barrel has its own unique preferences. But given Tikkas are known for being a shooter, it's a fairly safe bet any quality match ammo is going to be good. When I shoot factory, I bounce back and forth between Federal Gold Medal Match and Hornady Match, but that's more on whatever is around at that time.
For 1:8, you will likely find that anything in the 68 - 80 gr range will do good.
As for expected accuracy, that is up to you, Tikka does have a 1 MOA guarantee, so there is at least that.