Then I'd highly suggest adding Bikers to begin with. You can convert the bikers from the Dark Vengeance set pretty easily. When you look at running lists at 1000 Points+ I'd start adding the Heldrake. You've got the Oblits which is good. You can really solidify your army with Bikers, Terminators, Cultists, and Heldrake.
Personally, my favorite unit right now is Helbrute thanks to the Dataslate. If you get 5 of them you can choose their Crazed result before they move. It's pretty
OP right now for the games I play. But there are A LOT of Chaos players who can't stand the 'Derpbrute'.
At the end of the day though, you have to play an army that YOU like. If you want to do Iron Warriors, then run whatever it is the Iron Warriors prefer. Have fun, and remember: BLOOD FOR THE BLOOD GOD!