Nerg is dead! First attempt also! Enjoyed that fight.
Now I can focus on armour, but unsure what direction to take as I main Switch Axe.
The Nergigante switchaxe is good along with the armour. The best raw damage switch axe is the diablos axe of demons, you do need an elementless jewel to get the very best out of it though. For the Axe of Demons it can get to white sharpness with 4 in handicraft couple this with weakness exploit (dragon Eyepatch is best armour for this) at level 3 and you will be doing very good damage on crits. You can then focus anything else prioritising affinity then attack.
other jewels which would go really well would be tenderizer (1 point in weakness exploit) protective polish (does not lose sharpness for 1 minute after sharpening maintaining that excellent dmg boost from white sharpness)
Once you have a build like that you can start switching bits and pieces for specific fights eg Vaal gear or Miasma jewels to negate the effluvia debuff (cuts your health bar in half) Kushala gear to negate his wind attacks and maybe an earplugs set (needs to be level5 or nothing though) for the Bagel or when fighting multiple monsters when you could get chain raws.
FYI the nergigante switch axe will not benefit from handicraft as it cannot get to white sharpness, does have a large amount of blue though, concentrate on affinity/attack on that one with upping the dragon element.
Another really fun swax is the barroth grinder III which has good base damage and a hefty chunk of paralyse which is great in groups as you can all go to town if you have paralysed the moster.
I would try and get the Diablos Axe of Demons first off though as it will be useful against all enemies, and then build more specific sets.
Enjoy!