Ment
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As I understand it, sparks are reset, so you can't really accumulate them.
The system works like this: the Spark counter changes when the Gacha is updated. This happens around 13:00 Moscow time, and the day it happens is indicated in the Gacha itself. Usually, there are at least three days to accumulate enough resources for the roulette. But anyway, there's no point in saving up for the Spark before the Gacha, as the chances of getting gold are too low.
Regarding Lucio, he was recently available for the Spark in a Flash Gacha, a couple of days ago. If you're aiming for him, you'll have to wait for the next Flash Gacha, I suppose. The problem is that it will probably be in mid-January, and the roulette will be over by then.