I believe there is a God, or at least a higher power in the typical sense of it being all powerful, all knowing, omni-present, etc ; however, as of current, I wouldn't believe in a religion or doctrine to be more perfect than another.
Responding to your OP, the "Let us" verse is in reference to the Holy Trinity consisting of God the Father, Jesus the Son, and The Holy Spirit. All and One, as is depicted in doctrine. I believe in Holy doctrine as a guide more than an end all be all doctrine. It speaks differently to different people and I believe it's made to be understandable in nature, not 100% cold and factual; see parables (The bible could be one big parable). Plus, every religion from every time period believes their doctrine is the most true.
It's hard not to believe in a spiritual realm. Things happen that can't be explained by Science. People scientifically die and come back and are still themselves. Cells replace tens of times over, but a person still has a personality and personal values, despite them being a completely different person biologically, etc.
I believe God operates on higher frequencies, but I also think that we as humans underestimate the amount of power we hold over our own lives through manifestation.