[Coldsaturn]

Yes, so long as you don't have anything better, go with the blue protocores, but don't throw too many resources on them to level them up, focusing instead on clearing Core Hunt levels so you can get better protocores.
Needless to say, while your card stats are low, getting protocores that bump up full numbers is more useful than percentages, whereas with high level cards the opposite is true.

Also, protocores will sensibly increase stats in bursts of three upgrades per time, so that's what many of us do. We enhance thrice, see how things are going, and eventually decide to stop or go with other 3 bursts.