You are correct that the Bible (specifically lets say the NT) was not put together until the late 4th century. What I encourage you to do Emily, my daughters name

, is to start reading the early Christian fathers and look at the high regard they held the books that would become scripture. Starting with Ignatius, on up until the canonization of the Bible, the early Christian fathers appeal to what would become the NT. When a tradition or teaching is contrary to scripture and tradition, they confront it.
Now the thing about tradition is we all use it in certain things. You however are wondering where to find God's truth; scripture or tradition/scripture.
The first thing to point out is most of the traditons adhered to by Catholics, and to a degree the Orthodox, are things that are not part of the Bible OR early Christian history.
Take for example; the Assumption of Mary. What an event that would have been! The mother of Jesus swept away! The Catholic church teaches, for the most part that occured in Ephesus. Did you know though; no one mentioned it for 300 years? A bishop IN Ephesus even wrote that no tradition exists!
I encourage you to read the PDF file on my home page. It discusses at length how so many of the teachings of Catholicism are not found in the Bible and directly contradict early Christian history.
I can assure you that God's truth can be found. It is in the pages of the Bible. Sola scriptura is true and an examination of early Christian history will confirm that for you.