I've been going with a 3xCV/6xCL task force lately, paired with a 3xBB/6xDD fleet. I keep them together, but under separate commands. They decimate just about anything if they're of current tech. It's not hard to get Halsey and Nimitz up to a rank 8 command level within a couple months of war's start.
How do you level Naval leader so quickly? Do you use them to raid convoys? Naval experience seems to be the hardest for me to get