What are the highest damage outputs for a Warlock of the Fiend? (Pact of the Chain)

My now 3rd level tiefling Warlock of the Fiend just took the pact of the chain (Her familiar is a Quasit). So far I’ve found this to be effective:

Armor of Agathys (Now always cast at 2nd level: +10 temp. hp & 10 cold damage to anything that attacks her) +

Hellish Rebuke (Dexterity save, 2d10 fire damage on a failed save, or half as much damage on a successful one to a creature that hits her; 1/per long rest but still nice for a reaction)

+ Dark One’s Blessing after the Armor of Agathys disappears (Free temp. Hp for when she kills something = Charisma modifier + warlock level [7])

Her turn: Typically in combat, this means smoking everything in sight with Eldritch Blast; 1d10 force [+4 from Agonizing Blast] and if in a pinch, uses Cloud of daggers to catch several enemies at once.

Not too bad, I would say she’s able to pull her weight in combat with this, but I want to make her a heavier hitter. What are some of the best damage combos, invocations, etc for a Warlock?

Note: Can be answered for any level warlock, Knowing possible builds for the future would be nice, not just for 3rd level.