false life or mage armour

So im finally getting to play as the ever DM it's nice one of my players has been so interested with Netherdeep they want to have a have a go and run it. As my campaign was at a break point and my workload is mental I was happy to have a play for a while.

So our team sets off. A dwarf barbarian. A human paladin and me, the celestial warlock.

We got to level 2 and I'm trying to decide on my invocations. My character has no armour (choice). And is a eldritch blaster so I have agonising blast and have to choice my second.

I'm tempted with either armour of shadows or fiendish vigor

So which do you think is more optimal. Thanks all. Ultimately I will take character decision but good to know what might be more optional

From my initial idea seems to be the better option. Thank you Mage Armour seems to be my first intention you are all amazing.