Yo. I have a divine soul sorceror warforged and a couple cleric characters that might use necrotic damage spells like inflict wounds and so on. Is there a feat like elemental adept or something I can take that will turn any 1 damge rolls into 2s or something that can increase the damage on necrotic attack spells? 

No.

Quote from Cyb3rM1nd >>

No.

 Is there anything that isn't subclass specific that I can use to do more damgage with necrotic damage spells?

A mabaran ebony focus will give you a +1 to damage with necrotic spells.

Could be other magic items that would do something similar.

The only abilities I know of are the 6th level undead warlock that lets you deal an extra 1d8 and the 1st level death domain cleric feature that lets you target two targets within 5 feet of each other with necromancy cantrips.

Empowered spell metamagic.

1 spell point to reroll a number of damage die equal to your charisma modifier.

Quote from Bobbybaker >>

Empowered spell metamagic.

1 spell point to reroll a number of damage die equal to your charisma modifier.

 Thank you! I'll use this for my warforged Sorceror when they cast life transerence!