In the novel, they also found it fast enough, so he didn't intervene.
It was better for them to work hard to find it than just to think about it.
So, everyone kept practicing after resting, and then they practiced again.
Ashlee was also practicing with her knives.
So he was the only one who seemed to be relaxing on the rooftop.
"Ciel, why don't you also practice your ability?" Treyton asked.
"I'll try it later on after you find out how to train efficiently," Luciel answered while still playing games.
Actually, even though he was playing games, he was also training his abilities.
He was continuously gathering the energy of the plants in his surroundings and circulating it into his own, so his ability was actually growing continuously.
His ability was surely getting stronger faster compared to the others who hadn't found out how to efficiently increase their powers yet.
What they are doing right now is also correct.