Welcome to the game!
You have all the expansions, and everything you need to play everything as long as you have gametime. You are on an excellent realm. You are well set to go.
As far as I know, the devs are not allowing you, as a “New Player”, to play the expansions in order. The new rules, that were applied in prepatch a week ago, is that “New Players” MUST play through Battle for Azeroth to level 50 first.
After that, future characters of yours can talk to Chromie, outside the Stormwind Embassy or the Orgrimmar Embassy, and request to be placed in the timeline of any expansion to level.
You can check with Chromie now, on your Rogue, to see if she will talk to you
but I suspect she won’t.
If she won’t, you should proceed on your rogue to do the entry quests to Kul Tiras. When you have arrived in Boralus, check back in with Chromie again, and see whether she has changed her mind; I recall reading a post from somebody for whom that worked, though I can’t find it now.
Anyway, once you get to 50 you should for sure no longer be counted as a “New Player”.
At that point, I recommend you make one new character for each expansion. Blizzard have speeded up levelling enormously and tuned it so that any one expansion should get a character from level 10 to level 50.
So take one character, start it in its racial zone rather than Exile’s Reach, then at level 10 talk to Chromie and choose The Burning Crusade as its expansion. Make another character of another race, see its racial zone, and at level 10 choose Wrath as its expansion, and so on.
Although you can’t do the expansions in order (what does order even mean when you start in Cataclysm and go back in time to TBC and Wrath?) you can get a much more complete experience, and earn 7 maxed characters at the end, for as much time as it would have taken you to complete them all on one character before. While you might not want to queue for dungeons, and definitely will not find parties to do raids of each expansion, you can go back to see them on your level 50. A level 50 will be able to walk in to any dungeon or raid up to Warlords expansion and simply and easily solo the place.
P.S. I found the thread where a poster said that merely doing the start of Boralus in BfA was enough: