Mulligans
General Mulligans
Always save Renounce. Coils are good for filling your hand quickly with cards. Drain life and Shadow bolt are usually safe to keep. Acolyte is good for accumulating cards quickly except against very aggro decks (though maybe I'm wrong here). Keep hellfire against minion heavy opponents like shaman, druid or hunter. Keep Gluttonous ooze for weapon classes.
The goal is to accumulate cards in the early turns while controlling the board. The lower cost warlock spells and hellfire are effective at clearing early enemies. Once you nearly have a full hand then Renounce Darkness when the opportunity arrises. If I draw Renounce early, sometimes I hold off a few turns if I have nice warlock spells I can use. You want to focus on gaining cards because once you Renounce you burn cards quickly since they cost one less. If you get a class that’s spell heavy, then save low cost spells to combo with Gadgetzan. Violet is nice if you draw early because you can burn the warlock hero power and not lose health (same goes for hellfire and felfire). I omitted Jaraxxus because you often Renounce before you get the chance to use him. Alexstrasza is essential. Elise is also great for all the extra cards she gives you.
Suggestions would be much appreciated!
Thanks
ps. I was inspired by Savjz similar deck he was playing in high rank. It’s a really fun deck to play!