I would pass on Kharadron Overlords. They are pretty aweful atm.
Idoneth are one of the top if not the top army for Order Factions. Going Akhelian focused would be my advice. The eels are OP.
Ironweld Arsenal is more of a support army. Generally you see people play Grand Alliance Order or Freeguilds and bring IR for support. However, Freeguilds themselves are pretty solid right now.
Ogres are pretty a cheap and decently killy. You also only have to paint about 20 or fewer models for an Ironguts list, unless you decided to take Gnoblars (ironguts grots). Grots under the buff of an Ogre Tyrant do make for an amusing tarpit though.
Slaves to Darkness have a fantastic Start Collecting Box. Two of their SC boxes and then any other Chaos SC box is a decent start to a Chaos army. You will end up with a potentially superfluous Chaos Sorcerer Lord, normally one is enough.
Thee SC boxes of Beastclaw Raiders and you have your army. They a solid mid tier faction. They tend to either murder everything on the table or lose to the objective game though. Normally I don't enjoy my games vs them regardless of winning or losing.
You could build a pretty decent death army with the SC Box for Skeletal Hordes and Deathrattle Barrowlords box. But be prepared to buy many Skeletons... and paint them.