You missed the chance to get a pretty cheap Kushina a while back from Great Plates & I'm unsure of what she would cost you normally, but she is a decent pick & probably worth getting/the better option if you don't have the ability to bond mystery Minato.

So a few of us were able to get Minato from Sakura's Gift for 4-6k coupons, which is more than half the cost of what he usually is, that and the fact you can work toward his bond mystery if you have Kid Kakashi & Kid Obito it makes it possible for you to scale well as a F2P player, so yes Minato is a decent choice if that's the option you wish to take- because of his cost at the moment, assuming you can get it for 4-6k & it's not related to RNG luck, I'd definitely go for the Minato.