Heh
i think you should choose the "maximum points" limit of your army. Me for example - i got 500pts army, that includes core, support and one hero. Its only infantry though. But its not a bad start.
Soo you should think of it in this way "What do i want my army to consist of, and in what point limit do i need to squeeze in".
I personally would put in some Easterling warriors as core. They can wield bows and spear/pikes (phalanx rule), and if you want to cower more ground you should go for some of Harad mounted units (like serpent guard) and later on mix them with Cataphrakts.
The thing is - the mutiple strike rule makes bigger masses of units playeble. Soo basically what you want is to have some hard hitting stuff lilke, dunno lets say Amdur and a Dragon Knight, some D6 defenders - Eaterlings with shield, and some reinforcements who allow you to make full use of Phalanx and mutliple striking. Here come in the more wulnareable but cheaper Haradrim Warriors.
As for comand for Haradrim, they got some neat stuff (i like the sound of Hasharin, though i dont have him yet)
The Fallen Realms has insane variability of units. And if you feel that you lack some serious punch a Ringwraith (and especially a named Ringwraith) can do the finishing touch. Well i hope this helps you a bit when choosing the right units for your army. Good luck