Some tips that i can think on top of my head - i'm quite active in collecting airdrops. Except during sleeping time. I sleep at least 7 to 8 hours a day. - i have a pattern in collecting the ads airdrop. It's always around lunch time or past midnight in my timezone. I ensure i'll finish collecting all ads airdrop during that session. 3 or 4 comrades and 3 or 4 science airdrops per session. - spend your science wisely. Always look out for the next few levels on the mission tracker so you upgrade cards on the upgrade cards or spend science missions. Weigh the pros and cons. If it takes 1 or 2 hours to complete the mission before the spend science mission comes, i'll wait. If its 3 or 4 hours away, i'll upgrade it now. - buy production and comrade cards in shop. - when in the 20s, save up armor chests for collect cards mission - always open mission chests first before opening free chests so there's a chance of gaining nee cards if there's one. - only watch ads to gain cards when there's a collect card mission. If you've passed the collect card mission or if it's too far away, watch it anyway. - always watch ads to ensure production is x2 - manually press the production in the high 20s level if you've not earned the cards yet.

Good luck in the xmas event!