Most important quote from each of the 12 imams:

Ali Amir Al Mu'minin, the first:
"People are of two kinds: either your brothers in faith or your equals in humanity."

Hassan Al Mojtaba, the second:
"Generosity is to give before being asked"

Hussein Sayyid Al Shuhada, the third:
"Death with dignity is better than a life of humiliation / disgrace."

Ali Al Sajjad, the fourth:
"He whose soul is noble, the world is easy for him."

Muhammad Al Baqir, the fifth:
"The parable of a man greedy of this world is the parable of the silkworm: the more it winds the thread round itself the farther it becomes from salvation, until it dies of grief."

Ja'far Al Sadiq, the sixth:
"Patience is the peak of faith."

Musa Al Kazim, the seventh:
"Anger is the key to any evil."

Ali Al Rida, the eighth:
"Everyone's friend is his reason; his enemy is his ignorance."

Muhammad Al Jawad, the ninth:
"Take patience as your pillow, embrace poverty, discard lusts, and oppose your desires, knowing that you are seen by God."

Ali Al Hadi, the tenth:
"The world is like a market; one community reaps benefit in it while another one faces loss."

Hassan Al Askari, the eleventh:
"Fear Allah and be a credit for us, not a source of shame."

Muhammad Al Mahdi, the twelfth:
"I am the Mahdi… I am the one who will fill [the earth] with justice as it was filled with tyranny."