Browser games, they've nailed it. So if you're talking about gamification: this is what you ought to be talking about.
Your debug gems would recharge after watching a short ad.
Could you elaborate how?
Admittedly I don't play browser games, but is it as the parent comment says, trials in browser games are usage-based?
In principle yes. That's because you want your players to be hooked before you first present them with the prospect to pay for an advantage. So you ensure a specific action is ingrained in muscle memory before it requires payment.