How did Nick’s first impression on meeting Gatsby compare to his prior expectations of the man?

When Nick first saw Gatsby, he saw him as aloof...... solitary.

"But I didn’t call to him, for he gave a sudden intimation that he was content to be alone — he stretched out his arms toward the dark water in a curious way, and, far as I was from him, I could have sworn he was trembling."

We later learn that Gatsby doesn't stand aloof.

The first time Nick sees Gatsby he describes him as "standing alone on the marble steps and looking from one group to another with approving eyes. His tanned skin was drawn attractively on his face and his short hair looked as though it was trimmed everyday. I could see nothing sinister about him"