Last night, Lebanese President Amin Gemayel and his wife, Joyce--closely protected by elbow-wielding security people--circled the Vista International Hotel ballroom, shaking hands and accepting good wishes. Gemayel, in replying to the repeated question "are you encouraged," answered nearly every time with a hearty "Very."

Secretary of State George Shultz, answering the same question during his brief stay at the party, was equally to the point, equally fervent: "Oh yes," he said.

Gemayel's visit here ends this afternoon, and the Lebanese ambassador, Abdallah R. Bouhabib, last night's host, was upbeat about the stay. "Beyond belief good," Bouhabib said. "Our meeting with President Reagan was glorious. Such a very good meeting. I know how great is his commitment to Lebanon. Today, he was afraid of the shelling in Beirut.

"But he said he will help us to build a strong army," Bouhabib said. "They said that Lebanon could not even get recruits, but now, in a short time we have 12,000 more. We have surpassed our goal."

Rep. Mary Rose Oakar (D-Ohio), who had met Gemayel on two congressional trips to the war-devastated country, was equally buoyant. "A group of Congress members of Lebanese descent met with him privately after his official congressional visit this morning. I thought again that he is the one guy who could pull the country together. He has people from all religious sects in his cabinet. He knows how to work with different groups, especially because he himself served in parliament."

Oakar said Gemayel was looking for "moral support. And he feels that he needs American Marines to show that confidence, especially in the areas where the Israelis have pulled out."

Neither Philip C. Habib, chief Mideast peace negotiator for the United States, nor his replacement, Robert C. McFarlane, Reagan's deputy national security affairs adviser, were at the party last night, except in conversational allusions.

Oakar said, "I think the Lebanese have a great affection for Habib. He has made a real sacrifice of his health to take on this task. He's done a lot."

Morris Draper, Habib's deputy, who is also leaving the Mideast negotiations, was there with his wife, Barbara Hornig. "I'm looking forward to becoming acquainted with her again," he said. "I'm career Foreign Service, so I'll be going on to another assignment. First, I'm going to take a vacation."

Patrick Daly of the State Department protocol office stood in the receiving line introducing the 500 to 600 guests. "I don't know when I've seen the head of a country receive so many guests himself," Daly said.

Gemayel and his wife stood for more than an hour to shake hands in an official receiving line after he had made his friendly tour around the room.

Many of the guests, such as Selwa Roosevelt, chief of protocol, William A. Anawaty, an international attorney who lives in Washington, and Sheryl Ameen, an art dealer, were either Lebanese by birth or because of family ties.

The former Lebanese ambassador here, Khalil Itani, and his wife Aiche came to wish their president well; Itani was recently named Lebanon's ambassador at large. Samira Hanna-El-Daher, former Lebanese consul general in New York, received congratulations on her new post as ambassador to Japan.