what gear if your poor like me?
highest rune I own is like FAL or something

Insight for merc weap. Stealth smoke treachery merc armor, tal Tasha’s helm is a good budget friendly merc setup

switch to act 5 merc and go for high life leech. get life leech on helm and both weapons. for armor go for duriel shell or anything with defense/resistances.

he will be a tanky boy for you.

You won't get a cheap merc that survives in hell mode. Maybe in nightmare. Insight, any exceptional unique armor and life leech blood crafted helmet. Stealskull is something people throw away you can probably get free. Any unique helmet with life leech.

Depends what character to be honest.

You could do worse than obedience if you don’t need Insight.

Treachery armour is always good, Gully or Tal helm.

Ty