To whoever created the [Memory Imprint: Experience of Forming Domain] resource in the store, sorry but I have to delete it. Domain is something that will already be included in the story, look forward to it.
Edit: also to the creator of [The Seven Virtuous Sins], congrats on being first to break the 1,000,000 mark. You might find that the price is a bit high and the ranking has changed, this is what happens when words like 'infinite potential' and 'infinitely stronger' get thrown around. Lol, if you guys manage to buy it and go that route, you will win. God of Sin. Infinite power. No questions asked, you win.
Ah, good - my plan won't need changing then. My reasoning for saving the crystals was that there is no advantage to using them now instead of later - they aren't limited to a certain number per day - so it's best to use them at the end after training, when we can make a plan to the effect of "keep using crystals until either we hit the breakthrough point or run out", and plan for that around other sources of xp.
There's no daily limit true. It's a good plan, you can use them up and buy more if you get close to maxing the skill and just need that little push. Keep in mind that it's not an instantaneous use however, it takes time to drain the energy out of the crystal and cultivate with it. Let's say around two hours since this one is meant to have a small bit of energy in it.
Lastly, on a somewhat related note, I should mention that some bottlenecks can't be broken through by just adding more XP. If the Mc hits one of these bottlenecks, based on the point (moving from one realm to another most likely) they'll need to complete some special task, meet a certain requirement, or experience a specific type of stimulus to breakthrough.