Jutsu Drain

Jutsu are bred from a shinobi's ability to merge and manipulate their chakra (mana). Based on the complexity, or strength of a jutsu, it will consume more chakra. Grasping the complexity of a jutsu is handled by mana slots (explained in the reply below). However, some jutsus are complex but demand a small amount of chakra (like kirin). You can even intentionally add or reduce the amount of chakra you apply in a situation. If its an attack, a boost, a wall, or anything, the chakra spent will determine it's efficiency.

Jutsu are split into 3 categories
Attack, Defensive, and Spplementary
Attack jutsu do damage equal to 1/10th of the chakra spent
Defensive jutsu can stave off damage/effects equal to 1/10th of the chakra spent
Supplementary jutsu effects vary a lot more but the 1/10th rule still applies
-i.e. (50 chakra) heal 5 points, produce 5 crows, capture 5 people, etc.

Wisdom allows jutsu to be cast by spending less chakra, but by default, 10 chakra would equal 1 point towards whatever effect you're trying to reach.

Mana Slots
Mana slots have their own points. The amount of points in one slot determines a ninja's ability to call a jutsu to their mind. If the jutsu is too complicated (req. 4 points), and the ninja's highest slot has 3 points, they cannot focus their mind enough to execute the jutsu.

Example:
Everyone has 10 mana slots
A new genin starts with 5 slot points
You can divide those 5 points among your slots however you like
Slot points drain when you use jutsu, depending on the complexity of the jutsu
Every turn in battle, if not full, you can choose 1 mana slot to regain a slot point
If any points remain in the slot after using the jutsu, you can use the remaining points in a follow-up turn, but you will not regain your 1 point per turn

A way to look at the different ways to use this is:
1 1 1 1 1 -> this shinobi may only need d rank jutsu to perform well, so they make sure to have access in most cases
2 2 1 -> This person may have a more focused strategy while managing their chakra costs
4 1 -> This person may have a bait and switch strategy, using a small jutsu to prepare a finisher

Chakra techniques that must be maintained only use the initial slot points to activate, and that slot does not regenerate while it is active. Features like byakugan and sage mode also work like this. However, features are a step up and gradually drain chakra while they are active as well. Making these abilities live up to their history, since they usually require someone being pushed in order to activate.

Jutsu cost:
D - 1000
C - 2500
B - 5000
A - 10000
S - 30000