Gemili, who will compete in the 100m at the London Olympics, clocked a time of 10.37 seconds in his heat.
The 18-year-old former footballer will take part in the semi-finals on Wednesday with the final on the same day.
The women's 3,000m was won by Kenya's Mercy Chebwogen as she edged out Hiwot Gebrekidan of Ethiopia but Britain's Gorecka took an impressive bronze as she upped the pace of the race for the final two laps.
"I was here for a medal and I'm extremely happy I got it," she said.
"It was really hard to be leading the race for such a long time. I did so because the pace was dropping and decided to make the race hard for everybody."
The big surprise of the day came in the women's Shot Put though when Shanice Craft, ranked outside of the world's top 10, took surprising gold with a throw of 17.15m in the final.
Kenya's Geoffrey Kirui won the men's 10,000m after an exciting battle with Ethiopia's Philemon Cheboi who took the silver.