Purify breakthrough just increase the stats when you purify your equipment. The only time you should you do it is only when you are willing to spend a lot of money since the only time it is available, you'll have to spend a lot. It doesn't give out a lot of power in my opinion.

You can get iruka in two ways. You can get him in events or you can refine fragments when you have 5* ninjas.

It seems like you don't understand what we said. Purify is the last thing you want to focus on but that is going to happen if you spend thousands of dollars on your power. Just don't worry about it.