Studies of Manichaeism are still somewhat limited and our sources are few. What we do know about it often comes from its opponents, especially the former Manichaean Augustine of Hippo, who would convert to Christianity. Recently, we have found a number of Manichaean texts in a variety of languages, commonly in Syriac, but sometimes in Chinese, Uyghur, Sogdian, Greek, Latin, Parthian, or various Persian Dialects. These have been remarkably useful in deciphering Manichaean Cosmology and Philosophy, but our picture is still very much incomplete.
Compounding this is that Manichaeism, like many other religions that spread over a long geographical area in that era, was remarkably syncretic. While Manichaeism itself was primarily rooted in Judaeo-Christian Gnosticism, it absorbed aspects of Zoroastrianism and Buddhism into it during its formative years. Manī, the founder of Manichaeism lived in the Sassanian Empire and traveled through it from modern day Iraq to modern day Pakistan. In his travels, he almost certainly encountered Buddhism as he made Buddha prophet in his doctrine and took the monastic element from Buddhism. After Manī’s death, Manichaeism spread into Rome where it became one of Christianity’s main rivals, here, it remained rooted firmly in Judaeo-Christian Gnosticism, but it also traveled into Central Asia and China. In Central Asia and China, it absorbed the local gods and customs and took on more and more features of Buddhism. In China, Manī was known as the “Buddha of Light” and throughout Sogdia, Parthia, and the Uyghur Khaganate it existed in competition with Buddhism and was almost indistinguishable. Case and point, after the Tang persecutions of Manichaeism, the Manichaeans were more or less absorbed into Buddhism. For the most surprising manifestation of Manichaeism, we look to Modern Christianity. Modern Christian Philosophy has had few more important influences than Augustine of Hippo. His Confessions and City of God adapted Neo-Platonic principals and fused them with Christianity as well as addressing the nature of the soul, ethics, and the problem of evil. Few would deny the Platonic and Neo-Platonic influence on Augustine, but less ackgnowledged is the Manichaean influence. In his youth, Augustine was drawn to Manichaeism for it’s philosophical value and its clever answers to the problems of “sin” and “evil” through its dual nature. Augustine turned away from his mother’s religion of Christianity and followed Manichaeism having found the answers he wanted in it. In the middle of his life, he converted to Nicene Christianity and became its most prominent exponent. However, Manichaean pessimism remained in his works. Augustine asserts that evil is passed through the line of Adam, that original sin has created wickedness present in all. In his Epistle to Paulinus, he asserts that mankind as a whole, is wicked, which he expands on in the Opus Imperfectum, stating that only through the grace of God are the wicked allowed to be good. Furthermore, his interpretation of human history in The City of God reveals a dualist view of human history in the struggle of man to be light and good and free themselves from corruption and misery.
Sources:

Van Oort, Johannes. “Augustine’s Manichaean Dilemma in Context.” Vigiliae Christianae 65, no. 5 (2011): 543-67. http://www.jstor.org/stable/41480508.

Scott, David. “Buddhist Responses to Manichaeism: Mahāyāna Reaffirmation of the “Middle Path”?” History of Religions 35, no. 2 (1995): 148-62. http://www.jstor.org/stable/1062694.

Buonaiuti, E. “Manichaeism and Augustine’s Idea of ‘Massa Perditionis’.” The Harvard Theological Review 20, no. 2 (1927): 117-27. http://www.jstor.org/stable/1507588.

Miereki, P., & Bedhun, J. (Eds.). Emerging From the Darkness: Studies in the Recovery of Manichaean Sources (Vol. 43, Philosophi Antiqua). Liden, Netherlands: Brill. (1997).

Lieu, Sameul N. Manichaeism in Central Asia and China. Vol. 45. Nag Hammadi and Manichaean Studies. Leiden, Netherlands: Brill, 1998.

Dan, Jennefer Marie. Manichaeism and Its Spread into China. Master’s thesis, University of Tennessee-Knocksville, 2002. Accessed May 11, 2018. University of Tennessee Creative Exchange.

Tardieu, Michel. Manichaeism. Translated by M. B. DeBevoise. Urbana, Ill: University of Illinois Press, 2008.