Basic idea on combo math:

If each ninja has 1 Chase and you have 2 on your main, the most you can ever do is 6

So to get 10 you need to have multiple ninja with multiple chases.

Some ninja can chase twice (Pains, Chiyo Chikamatsu, GNW Tenten etc) with some of their chases, some ninja have multiple chases (Kakashi, Sasuke, etc).

Sasuke can chase 3 times, Main 2, other Nin 1 each equals 8 combo, for example.

Not all ninjas chase well off of each other, which is where summons come in. In order to hit 10 you are probably going to need a lot to rare ninja and/or Gold Summons.

Hope that helps.