What was happening with the Nazi Party during the years 1924–1929?

At the end of 1924, Hitler was released from prison after only six months. He had been imprisoned for his failed coup attempt, in which he attempted to take over control of Germany. From then on, the Nazi Party sought power not through coup but through legitimate means. Hitler was officially banned from making speeches, but that ban was lifted in 1928.
Although the Nazi Party was waning in these years, Hitler spent the time building up the party organization and propagandizing in any way he could. While election votes for his party fell, he nevertheless increased overall party membership. He created the SS as a personal bodyguard for himself and put Himmler in charge of it. Nazis infiltrated civil and cultural institutions to promote an Aryan worldview.
Hitler also used the time to curry support for his causes among the wealthy, who sometimes either believed they could use Hitler as a bulwark against communism or who actually endorsed his ideas. By the time the stock market crashed in 1929, the Nazi Party was poised to take over—which, as we know, they did in 1933.