Up until the crash, the stock market made a major surge in the 1920s. The Dow Jones Industrial Avg quadrupled from 1924 to 1929. A major aspect of investing during this period was margin buying, where stocks were bought with borrowed money. This is considerably more risky than buying a stock with money you don't have to borrow. It magnifies both gains and losses.
My perspective is that the era had few unaffiliated full time traders unlike today, when people trade electronically from home. Instead, a wealthy individual would form an investment firm to conduct full time investment management.
A couple of interesting biographies you might look into are Clarence Hatry and Richard Whitney. Both were famous investors of the era (both were crooks). Even better might be looking into Jesse Lauriston Livermore who is still respected today as an investor. His exploits were fictionalized in a 1923 book "Reminiscences of a Stock Operator".

https://archive.org/details/JesseLivermoreReminiscencesOfAStockOperator