If you really want to shoot 1000 yards, I would suggest you go straight to it. Get good equipment (you've already figured that out), and go for it. Instead of taking it in small steps (100y-600y-1000y), put on a thick skin, and do as much 1000y shooting as you can, as soon as you can, as often as you can. Having your head handed to you is _good_, if your ego can take it - how else are you going to learn what the wind does, and start to be able to do something about it?
I would suggest a .308 as your best first rifle, for the reason that it is not only capable of shooting well at 1000 yards, it is such a well-known quantity that it is one of the easiest to get shooting well at 1000y. Shooting any decent rifle well at 600m is a piece of cake, but to be honest there is a certain amount of rifle and ammo fussiness involved in getting a rifle to shoot well at 1000 yards. I would suggest that until you want to get into ammunition and rifle tuning for it's own sake, that you choose whatever is least fussy!
A .223 is also great, the only reason I would rate it second to a .308 is that it is somewhat more difficult to get first-rate performance from a .223 than a .308 at 1000y. Yes, it can be done, and essentially equal a .308 in performance, as well as being cheaper to shoot and even more fun too - but, see my above point about choosing the least-fussy option.
All the other higher performance cartridges are great too, though of course they have their tradeoffs (I am of the opinion that in an ideal world, we'd all shoot 6BR/105 instead of .308/155, in both TR and F Class - but that's not backward-compatible, and therefore not a practical suggestion). Generally they tend to be fussier than a .308 (though once you put in the effort, the performance of a first-rate F-class rifle at 1000 yards is a thing of wonder to behold).
maybe not quite that happy but close!
Ask 100 long range shooters (Palma shooter) what their load is and about 80% will give you that load.
