Get Six Paths Naruto as soon as possible, stock up on Advanced Trial Vials and Protections, and get him breakthroughed, because he'll be a huge help for Ninja Exam... and everything else because 6P Naruto is OP. Also get Wind Blade Asuma, because his damage buff is pretty useful for almost any team you build, well most teams and get that buff breakthroughed because it allows the buff to work at 70% health and above rather than full.

Best Breakthrough Set-up at the moment for 6P Naruto is the following.

Mystery: Y+1

Standard Attack: +2

Chase: Y+1

Passive 1: Y+1

Passive 2: Y+2