Free 3K CC will be given if you're able to obtain the specific amount of Legends Festival Medals,
200 Medals - 1K CC
400 Medals - 1K CC
600 Medals - 1K CC
I know it is ridiculous to farm such Medals in Raid and it's not a guaranteed drop in every finished match, but there's a much more simple and easy way to farm those damn Medals.
Go to PVP, and use a Hero Unit or the Weakest Unit in your Character List just one unit. Then, enter a Friendly Match (No Deduction of Battle Points for Rank just a fan way to play with other players online with 14 Star Units).
Just purposely lose the match it'll be easy as every match is almost a guaranteed drop. I was able to farm 200 Medals within a hour and a half no joke. Then, if you keep losing purposely you'll eventually come face to face with BOTS all over until you win a match.
How to know if your opponent is a Bot? The, player doesn't have any Guild and their Title will be more on the basic ones and the flow of the match will be smooth unlike when you're facing a real player then there's some delay and lag.
I know what you'll say, this is a cheap ans stupid way but let's be honest not everyone will be able to grind that much and put such a lot of time for the game. They really made it more difficult to obtain and the drop rates for the Medals are pure nonsense mates.