Monks have a unique spell casting ability. Giving them access to the bard, druid, cleric, sorcerer, and wizard spell list. A shinobi can learn spells at half their level but can only prepare at 1/3 level. So a level 4 shinobi would have learned 2 spells but can only prepare 1. As well a lvl 10 shinobi would learn 5 spells but could only prepare 3.

 

Ginni

Meets the basic requirements to become a shinobi.

Shinobi expertise you gain prophenency in acrobatics and athletes. 

Shinobi casting. Starting at 3rd lvl you learn 1 cantrip and 1 1st lvl spell. you learn spells at 1/2 your class lvl but can only prepare spells at 1/3 your class lvl. You gain one cantrip every class feature.

All shinobi are adept at throwing weapons. You gain advantage with ranged attacks at 'short range'

Ki spell cost. All spells require ki points equal to 1 ki + the spell slot + 1 extra at additional levels. (3rd, 5th, 7th, 9th. Additionally any ki spent on a spell lvl 6 or higher can only be restored by a long rest. Cantrips cost 1 ki.

Basic shinobi spells. At 3rd lvl you can cast jump water walk and spiders climb on yourself for 1 ki. All spell casted in this way must maintain concentration and have a duration of 1 minute per ki.

Chuunin

Gain 1 cantrip for a total of 2

More advanced ninja gains more spells and can use summoning scrolls. You can have 1 of 3 types of scrolls at a time 

Weapon Scroll. You spend one hour x the rarity of the each item to capture weapon(s) in your posession into a scroll. You then can use you bonus action to summon the item(s) on your person. After summoning the items you can put all items that were originally sealed within 5 feet of the scroll. And recapture the item for 1 ki as an action 

Summon Scroll. You preform a ritual to capture one creature into a Scroll who's CR rating is equal or lower than the druid's Shapeshifting table. The ritual takes 1 hour x the CR rating. Once the scroll is used to summon a creature the scroll turns to dust

Spell Scroll. You spend 1 hour x the lvl spell. You can copy one spell you know to a Spell Scroll. You spend ki points equal to the lvl requirements of the spell. You can activate this scroll as a bonus action by spending 1 ki point. It does count as a spell used for your turn. You can not copy spells that consume material components. Also you can only active a scroll with spells that you know. When you activate the scroll it turns to dust

Enhanced Ability. You select one spell you know that is 2nd lvl or lower and has a range of self or touch. This spell doesn't count as a prepared spell, and you can cast it on yourself for 1 ki.

Jounin

Gain 1 cantrip for a total of 3.

You are able to have 2 summoning scrolls at a time. Note that you may only have 1 type of scroll at a time.

Signature Move. You select one spell you know that is lvl 3 or lower. This spell does not count as your  prepared spell. You can cast the spell at 3rd lvl for 1/2 of the ki rounded up.

Tijitsu.  when you use your bonus action to activate a Scroll, cast a spell, or make a monk strike. You may spend 1 ki to preform flurry of blows, patient defense, or step into the wind. Note you must do this immediately after you active the scroll.

 

S-Class

Master summoner. You can now have 3 summoning scrolls at a time 

You gain an extra cantrip to a total of 4

All spells lvl 5 and under cost one less ki. Including your signature spell and excluding your enhanced abilitie.

Your ki flows through your body constantly. Giving you resistence against bludgeoning slashing and piercing from non magical damage.