I've found that it's best to play when you see others succeed. If you don't succeed quickly yourself, then stop and try again in half an hour or an hour. The luck seems to be somewhat controlled on the server end, from what I can tell. Streaks are common and you can tell the lucky times based on how many people are popping up on the server-wide display.
When I ignore my own advice, I find that I waste 5 million coins or so and receive nothing. When I strike after I see that the runes are falling like hotcakes, I can get some fragments and maybe a yellow or two before luck runs out.
It's good practice to remember this game is not a sprint, it's a marathon.
