At the end of chapter seven, Gatsby "came into his own" he was complete.Before that he was a rich man with everything--position, money, ambition, reputation. But he was missing one essential element, a woman who could equal him in her beautiful looks and innocence and who could fit into his world. At the end of chapter seven Nick leaves them alone at Gatsby's home.It is like they don't even know Nick is there because they are caught up in their own little world. This is the rapture where they are everything to each other.
Chapter 5 of "The Great Gatsby" is where things start to come together in the plot. All of Gatsby's actions so far have led up to this momentous meeting with Daisy. You can imagine how he must have felt at the beginning of the chapter, being so close to his goal: he was nervous as all get out! Take a look:
"[Gatsby's] eyes glanced momentarily at me, and his lips parted with an abortive attempt at a laugh. Luckily the clock took this moment to tilt dangerously at the pressure of his head, whereupon he turned and caught it with trembling fingers, and set it back in place. Then he sat down, rigidly, his elbow on the arm of the sofa and his chin in his hand."
So, at the beginning of the chapter, Gatsby is acting like a little school boy instead of a rich, sophisticated, educated adult.
But your question is "how was he acting by the end of chapter 7," so let's take a look at that:
"As I watched him he adjusted himself a little, visibly. His hand took hold of hers, and as she said something low in his ear he turned toward her with a rush of emotion. I think that voice held him most, with its fluctuating, feverish warmth, because it couldn’t be over-dreamed—that voice was a deathless song.
They had forgotten me, but Daisy glanced up and held out her hand; Gatsby didn’t know me now at all. I looked once more at them and they looked back at me, remotely, possessed by intense life. Then I went out of the room and down the marble steps into the rain, leaving them there together."
By the end of the chapter Gatsby is in his own element (his sweet mansion) and is much more comfortable. He is calmer, and more comfortable with Daisy. While he desperately needed Nick as a crutch and buffer before, now he lets Nick go with barely a glance. This is Gatsby calm, collected, and in charge of his destiny.