Best value pack in Clash Royale if you only buy one

Writing this up while it is fresh, because I will forget the details otherwise. The thing that keeps tripping me up is that everyone assumes you already know the basics, and the wiki is out of date.

Half the advice online is a year out of date, which is why I wanted a current thread. I will report back once I have tested it properly.

For what it is worth, the community guide covers this better than I can, but the summary is to prioritise the basics first.

Worth a shot before anything drastic.

The usual fix here is nine times out of ten it is a driver or a background process, not the thing you suspect.

Only partly related, but that behaviour is intentional, even though it is poorly explained in-game.

The usual fix here is the wiki number is theoretical; real results are always a bit lower.