Well, that IS exactly the advise...
To play Araby at 1k you WILL need to adhere to the minimum compulsary units. So those you must buy anyway. And you dont want to buy more of those then the bare minumum in most cases.
Buying one each of all other units will start your army with some choices to spare, which IMHO is what you will need to learn when handling the army (any! army).
Remember this is aWarmaster, so there are no uberunits and there is (hardly any) listtailoring...
The only "extra" unit, other then the basics for 1K I would invest in is the unit you plan to use for the mirage spell.
Araby shares a trait with Empire, in that it is an army with a multiple choices in each of its strategic slots. You will need to learn how to play with a mix of foot, cavalry and artillery. Having access to all different unitsat 1k will allow you to figure out what combo´s work for you.