Beck's plan was shared by his acolytes (henceforth referred as the "Mysterio gang"). The Mysterio gang was only comprised of former humiliated / dejected Stark Industries employees. Their main point of contention is that Tony Stark is remembered as a saint for his sacrifice as Iron Man against Thanos (getting whole street paintings, etc.), even though he built (from their point of view) his whole super-heroic career on his employees' back (demonstrably false) and treated them as punchlines to his own jokes (which, yes, was 100% asshole-ish). There's also a few of them who were fired when Stark Industries flipped from weapon-makers to... whatever they do next.
Their main goal, achieved at the middle of the movie, is to coerce / manipulate Peter into giving up EDITH, who is the key to Tony Stark's kingdom. Their con was extremely long-winded, but as they note themselves, they had to fool Nick Fury himself (who was actually Talos, but Beck didn't know that) to ensure everything went fine in the long run.
By getting EDITH, the Mysterio gang finally gains back control on their own inventions and creations. However, Beck has a grander plan : entirely replacing Iron Man in popular culture and the public's mind-space. By fighting off supposedly tangible, spectacular threats all around the globe, Mysterio would have appeared as a "new Avenger" type of hero. An international saint saving lives better than Iron Man ever could, with even better publicity. I guess the Mysterio gang also wanted to reap the rewards from world-class popularity.
Less factually, I also believe Quentin Beck specifically wanted to persuade Peter Parker into giving up his super-hero career. Beck sees Peter as a fake messiah, a strawman chosen by Stark to inherit his wealth and resources even though they had no former bond, nothing. When receiving EDITH, Beck says :
Quentin Beck: [to Peter] You’re right, you may not be ready, but this is my responsibility.
Beck believes Peter doesn't have the shoulders or legitimacy to continue Iron Man's legacy. He is persuaded he is the only one worthy of incarnating the next "big" superhero. As he says himself right before the final battle : "Who knows ? Perhaps I'm gonna be shaking the Queen's hand in 5 minutes" (paraphrased).
TL;DR While the Mysterio gang mainly wanted to wrench Stark Enterprises' resources away from Peter and reap the fruits of their own labor (with some large extras), Quentin Beck also had a gigantic ego complex and wished for Iron Man-levels of popularity.