First, I would just like to say thank you for doing what you do. Why are there so many denominations and who is to say which one is right? They all believe in God and Jesus, yet all have different ways of praising and teaching. This can become very confusing to someone, such as myself, who is new to Christianity. Your insight would be greatly appreciated.
I can understand your confusion. I knew a man who was preaching to people in one of the African countries. He says at least one person told him, "When you Christians can agree on what Christianity is, then maybe I will listen to you."
Why are there so many denominations? A brief history of Christianity shows that over time men started binding doctrines on the church that were not in the Bible. As soon as somebody disagreed with the new idea, one or the other would take their followers and form a new denomination. Sometimes they would be named for the idea they promoted (Baptists, Sabbatarians, Presbyterians), sometimes for the men that supposedly led the change (Lutherans) or for the country where the change was proposed (Anglicans). Sometimes somebody else gave them a name that stuck (Methodists). Others chose names taken from the Bible (church of Christ, Church of God). I am using these names as examples, not necessarily saying that they are wrong. Of course, Christians were called Christians and nothing else, but with the growing number of distinctions between Christians, some have chosen to take names not found in the Bible.
Some groups wanted to "reform" the Catholic Church, which had itself gone away from scripture in some ways. This is called the Reformation Movement, which "started" with Martin Luther and others in Europe in the 1500's. By the 1800's in America there were some who said we didn't need to reform the church so much as restore the church to what it was in the Bible. This is the Restoration Movement which resulted in the churches of Christ and the Christian Church as we know them today. Their idea was to return to the church of the Bible and to "speak where the Bible speaks and remain silent where the Bible is silent."
Who is to say which one is right? Only God can say that. We can do what we can to determine which is following the word of God most closely and associate with them. The way to do this is to read the Bible and examine what each group teaches. There is scriptural basis for this. In Acts 17:10-12 the people of the town of Berea were called "more noble" because they searched the scriptures to find out whether Paul was teaching the truth. It may not be possible for you to find any one group that believes wholly as you do when you read the scriptures. Associate with those who agree most closely.
I, of course, would recommend that you find the nearest congregation of the church of Christ. Over time I have found them to be the closest to following the scriptures. I would generally avoid those whose congregations are a part of a larger organization, as the scriptures teach each congregation is independent. I would avoid those who teach that the Bible is not sufficient, but that God speaks to their members directly. I would also avoid those that teach that all you have to do to be saved is pray to God to come into your heart (rather than requiring immersion in water to figuratively "wash away your sins," as the Bible puts it). I would recommend that if possible you attend more than one congregation of any group you finally choose to associate with, in order to find a congregation that fits you best. This may not always be possible unless you live in a metropolitan area.
But don't listen to me, so much as to the Bible. Read and study, and then determine who God wants you to assemble with.