I've been asked several times from either new warlocks or old warlocks who came back to the game about what addons are out there to help a PvE warlock. Recently, it's been through Twitter, which isn't exactly the best place to explain how to get the most out of your UI.
Gear is one important preparation for raiding, and I've set you up with most of those considerations. Knowing your class and spec is another, and I promise, I'll get to that. But a good buff to your spellcasting techniques is a well-done user interface, so let's talk about that.