I think the idea of a "bare minimum" is somewhat troubling in itself. I don't know that Christianity can be reduced to a bare minimalist set of things or thing.
The bare minimum could be said to believe that Jesus of Nazareth is the Christ; one can't be a Christian (after all) if they don't believe Jesus is, indeed, the Christ, i.e. the Messiah.
That of course isn't necessarily sufficient, as there are other religions which believe this too, most notably Islam accepts the claim that Jesus is the Messiah. And Christianity has never stopped merely at that one statement, because there are certain fundamental ramifications of such a bold claim and surrounding, compounding issues: namely that if Jesus died, but did not rise, well then He's not the Messiah. We can only confess that Jesus is the Messiah because He stopped being dead, He rose from the dead, and among everything else this means it also means that Jesus' messianic claims are vindicated. If Jesus remained dead, and still is dead, well then He's not the Messiah because a dead messiah is no messiah at all.
Of course as we continue to work through all these things we realize that at some point a "bare minimum" almost becomes impossible--we see this work itself out in history itself; as Christians put their faith in Christ into words it required doing so in meaningful ways--and that often resulted in the various heresiological controversies of the early centuries, which culminated in the ancient ecumenical councils and the historic creeds of the first thousand years of Christianity.
Is the bare minimum Nicea? Nicea and Constantinople? Well how do we address the Nestorian controversy? The Eutychian controversy? The Monothelite controversy? The Iconoclast controversy? Etc.
We end up getting, rather than a "bare minimum", a rather robust, historic tradition of a living, ongoing faith of the Christian community. That itself gives us more problems, however, as sometimes that community has resulted in schisms. We can see that for example in the 5th century between Diaphysite (Chalcedonian) and Miaphysite (non-Chalcedonian) churches; the Miaphysites became what we call the Oriental Orthodox today, and the Diaphysite became what we call the undivided catholic and orthodox Church--until there were further problems, such as the 9th century Photian Schism which was kind of healed until the 11th century and the Great Schism took place, and then the Great Schism was effectively finalized by the events which transpired in the [Western instigated] Council of Florence in the 15th century--effectively ending any chance of reunification between East and West. This means that we now speak of Roman Catholics and Eastern Orthodox. Not long afterward, in the West, the Lutheran reformers were speaking out about certain abuses, and also calling into question certain teachings which resulted in a papal condemnation of Luther and the Lutherans, with the Lutherans then largely accusing Rome of acting as antichrist, and so we get another schism there, and of course then there is the significant differences of views between the Calvinists and the Lutherans, and also with the Swiss Reformed (Zwinglians), and the uniquely British schism with the formation of an independent Church of England. And the eventual explosion of Protestant, quasi-Protestant, and neo-Protestant sects of the next few centuries.
Which then gets us to a point where we want to ask, "What is the bare minimum?"
And that really is a hard question. We can make certain decision for the sake of functioning together in a medium such as here on Christian Forums, the Christians-only sections require subscription to the Nicene Creed (with or without Filioque) and a Trinitarian belief--that is helpful as a kind of bare minimum so that Christians from across traditions and denominations can come together to discuss other topics. That works here for the intended purpose, so in that case a "bare minimum" may just mean for what purpose.
Because if the ultimate purpose of a bare minimum is "what do I need to do and/or believe in order to be a Christian (from God's POV) and to be saved" which is effectively what is being asked in the POV then you're going to ultimately get very different answers from different Christians.
As a Lutheran I'd say that you don't do anything yourself really, God does it for you, objectively by the death and resurrection of Christ, and that God unites you to this objective reality by granting faith to you through the Means He has established: Word and Sacrament; that by the hearing of the Gospel, in the waters of baptism, etc God works faith in you and through this faith you have been saved and are in fact being saved. It is these gifts from God which make all the difference.
That isn't the sort of answer you'll get from others, you may not get that same answer from anyone who isn't Lutheran.
On some level one is going to have to make some sort of commitment to a confession and conviction, that may change over time, because one may be convinced of a different perspective; but fundamentally it boils down to that conviction and confession--and it may be right or wrong ultimately, we don't know, we're making our stand on faith not certainty. And, ultimately, then, simply trusting in God to be merciful to us sinners.
-CryptoLutheran
Proverbs 3:5-6
