The highest level "Ninja" monster is "Twilight Ninja Getsuga, the Shogun" with level 8. This monster as a tribute would allow for the highest possible summons with this card's effect. It can basically summon ANY Ninja from the deck.
If you are willing to use "Armed Ninja" and "Crimson Ninja", tributing a level 4 "Ninja" for this card will allow you to summon 4 of them. You can then use their effects to clear your opponent's back row and then either use them as Tributes or as Xyz Materials.
During the Battle Phase, if you attack directly with "Senior Silver Ninja", do you active this card tributing the monster and special summon "Red Dragon Ninja" for an additional attack.
You can use this card to dodge traps and attacks, at the cost of tributing your monster for another one.
You can tribute any level 4 Ninja monster for another level 4 Ninja. This means you can trade out ninjas, dependent on what kind of effect or ninja you need. Ex. (Play 'Dupe')Tribute Masked Ninja Ebisu, special summon Ninja Grandmaster Hanzo, activate Hanzo's second effect. Then play another 'Dupe' -> tribute Hanzo -> Special summon Ninja Grandmaster Sasuke.