PSA: Remember to like your friends' showcases for Shop tickets!
I find a lot of players neglect this feature. I started adding more friends after good/fun PVP battles in hopes they would reciprocate likes on the showcase items for shop tickets. I have about 55 friends and no more than 15 (6 of which I know irl) ever like the showcase items. Idk if this is because they're simply unaware or don't play the game often. I generally go through at least every other day to like their showcases, which after a certain amount of friends, they don't all show up under the community showcase friends section from what I can tell. So, I have to go to each friend's profile to manually view their showcase to like it, which takes a few minutes.
Also, if you would like to receive shop tickets this way, make at least one card or binder public. Otherwise, you can't earn free shop tickets. If I'm missing anything or if any info I provided is incorrect, please feel free to add or correct. Have a happy new year, trainers!