Activity, communication, and city networks is key in this game too! If you're looking to get started, I hear 'Revolt' is an easier approach, as it gives you an extra 12 hours to defend against an enemy gunning for one of your cities. However, I personally like CQ/Conquest because it's more dynamic & involves more timing/strategy. The best defense, is well timed offense.
Goal for newer players: Learn how to move your troops and snipe w/ them. Timing is key in this game, and there's a factor called an 'anti-timer' mechanic making it a bit harder to time.
You can fight a good fight for 4-6 hours, but when you don't tend to your cities, 1-2 weeks worth of troops can be lost within 15-20 minutes. Intel is key, so the more you attack, naturally the more intel you'll receive. (Also look into index'ing tools, and other tools like GRTC to make maneuverability easier!)