Pretty much what LiveWaaaagh said.
I'd definitely advise hammerers, more gyrocopters, rangers, runesmiths and an army standard bearer as a priority for the first round of additions.
I'd rate hammerers above iron breakers on the basis that they can have a more expensive banner, so can have either the runes of Groth One Eye or Valaya, both of which really support the rest of the army really well. I find iron breakers pretty situational - they're brilliant against elves - but the amount of damage they can do is hit-and-miss. Iron breakers certainly benefit from having a runesmith with them to boost their damage output. However, if you use a lot of great weapon warriors in core, Iron breakers might be more useful. I tend to use a lot of hand weapon and shield longbeards, so hammerers complement them nicely, but as you've got more GW warriors, iron breakers *might* be more useful.
I quite like running 2 units of hammerers if the points allow - a big unit to smash the enemy, and a small one to provide support (and carry either the rune of Groth One Eye or Valaya). However, for main battleline units of hammerers, you do need to have huge numbers - as in over 30. They die as easily as a normal greatweapon dwarf, and every ranged weapon will target them, so they usually get badly shot up, and they always strike last in combat, of course.
Gyrocopters are for me essential - they're good value for points and are really irritating to the enemy. Also, if you've got Groth One Eye nearby, you can have interesting shenanigans with stubborn gyrocopters - with T5 and 3 wounds, they're hard for S3 enemies to get rid of, and they're ranged damage output is pretty decent, meaning that the enemy will often shoot them before your hammerers (which in my armies at least are the real threat).
Rangers are just handy. They're good value for points, and give you plenty of options (miners are the same).
Rune smiths are vital to dulling the enemy magic and adding a bit more bite to units which do not have great weapons. And an army standard bearer will keep you in the fight, and (with the Rune of Grungni) will offer a bit of shelter from shooting.
So for me, I'd go:
- Rune smith and army standard bearer
- Either hammerers or Iron breakers - depending on how you want to play.
(in that order).
It's great to see more 8th edition players around, and welcome to the forum.