you can do lvl1 -90 and you will miss nothing, once you get to 90, activate the WoD trial on all accounts at the same time and you get 14 days of sub, and access to WoD, you can lvl to 1 exp from lvl 91, and do all the stuff on the first zone (garrison stuff) this way you can practice parallel garrisons before you upgrade.

(you will spend most of your time inside the garrison which is not boxing friendly at all, still there's some way around limitations with addons and such. better get used to garrison life before you upgrade.