Background:
Well what I know about my clan is that before the founding of the ninja villages, us Uchiha were one of the many mercenary clans for hire. Because of our Sharingan as well as battle prowess, the Uchiha clan came to be known as one of the two strongest clans, the other being the Senju clan. The Uchiha clan originally is founded by Indra Otsutsuki, who was the one who inherited the Sage of Six Path's eye.
The Sharingan is a Doujutsu KG that can only be used by the Uchiha clan. However, the abilities of the clan aren't granted at birth. To unlock the ability one must go through a situation that is basically do or die, or being nearly beaten to death will one activate the Sharingan because of the requirements that it takes to be activated. It can have very incredible power to go with it but it depends on the stage of the Sharingan. Normally when a person awakens the Sharingan they gain 1 Tomoe, or depending on whats going on possibly another stage. Having the Sharingan activated drains little chakra, BUT, if a Sharingan has been stolen or given by someone one can't deactivate the Sharingan; they would have to cover it up by bandages or keeping their eyes closed to avoid chakra depletion i.e Kakashi and Danzo.
Having saying this, the Uchiha have three stages of the Sharingan Tomoe. Once one person reaches a new tomoe it remains that tomoe upon activation, so if someone has had 3 Tomoe when they activate it, its automatically in 3 tomoe mode.
First Stage, 1 Tomoe - The weakest stage of the Sharingan is the first tomoe of it. Granted when one goes through a situation thats life or death or facing a traumatizing thing and goes in an emotional state. Once this stage gets activated it allows the user to perceive motions and see chakra. The user can track speeds that would only be seen by a higher ranked, more experienced ninja. They also gain the ability to see through visual low rank Genjutsu and can follow the movement of most taijutsu moves done by normal Shinobi, even those faster than the user.
Second Stage, 2 Tomoe - Unlike the other time, you don't need to go through pain to get to the second stage. By training and honing your skills/abilities with Sharingan you can awaken it further. This stage allows the user to perceive motions more than before and copy the motions perceived with the Sharingan. You are able to anticipate and analyze faster movement more, as well as mimic minor movements made by an opponent such as physical contact moves. Can also track people 2 times faster than before, being able to read the hand seals the opponent is performing almost perfectly. And having the 2 Tomoe allows the Sharingan to see through a more advanced Genjutsu (C-Rank).
Third Stage, 3 Tomoe - By honing the skills in Sharingan the user awakens the 3 Tomoe. It allows the user to perceive track speeds and motions at an even higher rate than before, which gives the user powerful predictive abilities. It makes movements of others seem like slow motion to them. And it also allows them to see through Genjutsu way more powerful than the other ones (B-Rank). They can mimic basic Taijutsu, as well as copy hand seals that is performed by the enemy. This level of the Sharingan also has the ability to hypnotize the enemy and put them in a Sharingan Genjutsu.
Allow me fam.