-In the short term, if you need Iruka, it's worth using the refine functions to get to him, and even get him to 4* or 5* without spending coupons.
-Not too sure how the timeframe is for other skill-breaks, but if you do some research, and you would wish to skillbreak them in the future, save the fragments.
-If you are going way longer term, and wish for Naruto 9 tails chakra, you can just gun for that. Main character frags have little use else other than refining (as far as I know!).