Preparing For An Event
1) Concentrate mainly on offense. This is my professional opinion after playing this game for many years. I used to be one of the players who would upgrade platforms and defenses to level up fast, but this is not what you want to do. Offense is the key to getting the best prizes, if your offense can hold up, then you have a much greater chance at getting what you want. Upgrading offense is even beneficial to your defense, since you can add troops into your base, the stronger the troops, the stronger your defense.
2) Save up powerful Special Ops, I didn't do this last event, but I had a couple scorpion kings and they were beyond helpful, without them I most likely would not have gotten everything I wanted. Don't waste your time saving up the small spec ops, use those to farm 35 for rare offensive spec ops, also don't forget to reroll this makes a tremendous difference. The raptor spec ops works really well when farming for rares, all you do is take out the command center then end the Attack.
3) Level up missiles and fill the silo to capacity, missile are a tremendous help in taking out the key points of an enemy base, without those key points a base will fall apart making it easy for you to finish the job.
4) Fill metal, oil, and thorium storages to capacity, this helps in healing your troops, creating much needed mercenaries that work amazingly on island bases, and making much needed missiles
5) Probably the most obvious, give time to be able to heal all your platoons before the event starts, the more you have to heal during, the less xp you will get overall
6) Take your time, when it comes to the actual event, don't rush. Rushing could, but won't always, be your downfall. Keep the wiki close by when a units range is questionable, if U can't assume the level then assume the highest range for that unit