What is an overview of Lutheran faith-alone systematically taught before Martin Luther?

As I begin to answer your question, please note that it is not clear. Your question addresses the issue of faith (the third 'sola' of the reformation, "solā fide"). But as you flesh out your question it seems clear that you are really talking about the first sola ("solā gratiā"). The two are distinct from each other. The first ablative use answers the question, "what would motivate God to save me?" The answer (Eph 2, et al) is God's grace (his undeserved love toward undeserving sinners) is the only motivation God would have to save us. The third ablative use of the Reformation, "sola fide" answers a different question: "What tool does God give to me so that I can have, hold and understand this salvation?" (ⲟⲣⲅⲁⲛⲟⲛ ⲗⲏⲡⲧⲓⲕⲟⲛ). From here I will assume you are not speaking about sola fide, but instead, sola gratia.

Though the question pops up here and there in history, Luther was an Augustinian monk for a reason. Augustine, in his dealings with Pelagius, arrived at a view that we call today, "by grace alone." For a good paper dealing with Luther and Augustine, you can read through this essay: http://www.wlsessays.net/bitstream/handle/123456789/2645/KoesterGrace.pdf?sequence=1&isAllowed=y

Though Birdie's answer seems to give an accurate overview, I feel there is a need to add some details regarding Victorinus and Augustin as evidence to address the question deeply.

Luther's sola-fide or faith-alone doctrine is defined as monergism which means man's efforts are vain, as he is totally incapable to be righteous; and the idea that no one was ever justified by the Mosaic law. It is based on the interpretation of Paul's arguments against works of the law can imply not just the Mosaic-covenant works but any effort to please God. I found a reference of Augustine of Hippo (5th century AD) that suggest the Lutheran interpretation. Augustine interpreted "works of the law" arguments can apply to moral-works in general - On Nature and Grace

Chapter 2 [II.]— Faith in Christ Not Necessary to Salvation, If a Man Without It Can Lead a Righteous Life

Therefore the nature of the human race, generated from the flesh of the one transgressor, if it is self-sufficient for fulfilling the law and for perfecting righteousness, ought to be sure of its reward, that is, of everlasting life, even if in any nation or at any former time faith in the blood of Christ was unknown to it. For God is not so unjust as to defraud righteous persons of the reward of righteousness, because there has not been announced to them the mystery of Christ's divinity and humanity, which was manifested in the flesh. 1 Timothy 3:16 For how could they believe what they had not heard of; or how could they hear without a preacher? Romans 10:14 For "faith comes by hearing, and hearing by the word of Christ." But I say (adds he): Have they not heard? "Yea, verily; their sound went out into all the earth, and their words unto the ends of the world." Romans 10:17-18 Before, however, all this had been accomplished, before the actual preaching of the gospel reaches the ends of all the earth— because there are some remote nations still (although it is said they are very few) to whom the preached gospel has not found its way—what must human nature do, or what has it done— for it had either not heard that all this was to take place, or has not yet learned that it was accomplished— but believe in God who made heaven and earth, by whom also it perceived by nature that it had been itself created, and lead a right life, and thus accomplish His will, uninstructed with any faith in the death and resurrection of Christ? Well, if this could have been done, or can still be done, then for my part I have to say what the apostle said in regard to the law: "Then Christ died in vain." Galatians 2:21 For if he said this about the law, which only the nation of the Jews received, how much more justly may it be said of the law of nature, which the whole human race has received, "If righteousness come by nature, then Christ died in vain." If, however, Christ did not die in vain, then human nature cannot by any means be justified and redeemed from God's most righteous wrath— in a word, from punishment— except by faith and the sacrament of the blood of Christ.

Did Marius Victorinus of 4th century taught sola-fide? NO

The view among some protestants that Victorinus was the early or first champion of sola-fide doctrine might have been caused by misunderstanding his phrase faith-alone in Galatians commentary. Victorinus did make clear distinction between moral good works and the specific Mosaic-covenant works. Here is a quote from page 292 of the book Marius Victorinus' Commentary on Galatians, by Stephen Andrew Cooper

For all who live based on works of the Law are under a curse (3: 10). Forcefully, then, he has added that not only are those who live based on works not blessed, but also that those who live based on the works of the Law are under a curse. Now, as he said based on works of the Law, let us understand that there are also works which belong to Christianity, especially those works which the apostle frequently commands (and also what has been commanded to him: let us be mindful of the poor) and the additional precepts for living which are included in this apostle’s writings. Each one of these works is commanded by the apostle to be fulfilled by every Christian. The works of the Law, then, are something else: religious observances, obviously, offerings of a lamb (although the Passover has now been fulfilled through Christ); and there are further works which they do as well, pertaining to circumcision and foods to be observed or prepared.