I think you’re operating at a distinct disadvantage.
The deposit of faith, i.e., Divine Revelation, was given by Jesus Christ to mankind through the Apostles, and their successors, the bishops, for 2000 years.
SOME, but not all, of what Jesus revealed was written down. (see John 21:25) We call this the New Testament. There is much, however, that wasn’t written down, but passed on orally. We call this Holy Tradition. Both of these, however, must be interpreted by the Magesterium of the Church, the successors of Peter (the Pope) and the Apsotles (the bishops in communion with the Pope). Like the Trinity is three Divine Persons in one God, inseparable and perfectly united, so too is the Word of God transmitted to us by Holy Tradition, Holy Scripture, and the Magesterium of the Church. So, don’t get stuck believing that “unless it’s in the Bible, it ain’t true.” The Word of God is more than just the Bible, and much more than the Bible, personally interpreted. Like any book, it needs an authentic interpreter, which Jesus provided for us in the Church.
We do not “make up” these teachings, but only pass on what we have been given by Christ. We do try to explain these teachings in terms people can understand in the age and culture in which they live, but we never, ever change them. Never have, never will. We don’t claim the authority to correct Jesus Christ.
Now. That being said, when we talk about the “necessity of belief” of the teachings of Christ, this principle must be conditioned by the fact of the ability and opportunity of each individual. For example, not everyone has the same intellectual ability to understand certain things. Some can understand all the doctrines and dogmas. Some are still learning and haven’t covered them all yet. God, being infinitely just and infinitely merciful, would never require that of us of which we are incapable. What is required, though, is religious assent to all that the Church teaches, because it is all of what Jesus Christ revealed to mankind. In other words, an individual may say, “Well, I don’t really quite understand the dogma about the Immaculate Conception, but I accept the teaching from the Church because I know it came from Jesus, Who is the Truth.”