I was raised in a "trinitarian" church that taught basic oneness. Most trinitarians I know believe in one God just as much as I do, they just can't explain it as easily as they can explain that there are three manifestations or persons of God. I've heard oneness preachers say there were three manifestations and I sat there and laughed-There are many more than three ways that God has manifested Himself, if you want to be grammatically correct. I don't think that trinity is a damnable doctrine. I think human beings just have trouble expressing spiritual things in words sometimes. I do think that there is power in knowing who Jesus really is, but again part of that is because it always scared me to think that God would send someone else to earth to die a gory death while He sat up in some comfortable throne room playing chess with our lives.
What I believe is there is one God, manifest in the flesh through Jesus. Jesus, as God in flesh, died for us. God is a spirit, and generally in the Bible the terms God, Father, Jehovah, Yahweh, etc are used to describe this Creator spirit that is omniscient and omnipresent. Jesus is God robed in flesh. He is the physical manifestation of God to us. The Holy Spirit is the term generally used to describe the spirit of God working in us and through us. These are not three separate coequal, coeternal beings, but all one God, working in different ways. That's why its easy to see that the Father and the Holy Ghost are the same: God is Jesus father, yet the Holy Ghost overshadowed Mary, and she was found with child of the Holy Ghost. Oops? No, God in Heaven, Holy Ghost working in and among us. Same spirit, but different terms depending on location, just like you may be "daddy" at home, "sweetie pie" to your wife, "Mr. Smith" at work, and "Timmy" here.
The verses that seem to confuse things are those that say things like "God and our Lord Jesus". Try a counter example: Lucifer was the angel of light cast out of Heaven. The Devil or Satan is the same fallen angel working evil on earth. The devil isn't two or three persons, he is one depraved being named several different ways in the bible. Tell me what you think of
Rev 12:9 and
Rev 20:2. How many are there?