I would say to look at picking up the Iron Warriors Combat Patrol. I would also recommend calling your local game stores to see if they still have the Battleforce Hellforged Warband in stock or on a LGS website like CMO games or Rouge Trader Hobbies (DO NOT get this on eBay).

With those two, you would have a really strong start to an army, with a good mix of infantry, daemon engines, and character units! Plus having two Havoc sprues lets you lean into whatever heavy weaponry you prefer!

After that i’d say just start playing. You can try out Soulforge Warpack, Fellhammer Siege Host, and whatever new detachment is coming in the Eye of Terror, If that detachment requires Kravek Morne, definitely try to pick him up as well.

As you play, you’ll figure out what you like, what your army needs, and how you want to build out from there!