Most Important thing you need to win battles

Opinions vary about what is the most important thing you need to win battles and skirmishes in Facebook Fleet Command , Some say pack your fleet with the most expensive unit , some say that a balances statistics is the key to victory , but for me the most important thing is the freshness of the crew. Even if the enemy fleet have a slight advantage over you if your crews state is better than there crew status you have more than a fair chance of winning that battle or skirmish.
My usual strategy is update the captains statistics and update 2 stats of the crew. Do the battle and the skirmishes for that round and rest the crew from the final training point. So whenever I visit the game again my crew is always fresh.
What do you think is the most important thing in winning battles and skirmishes ? Feel free to share your thoughts in the comments section.