I. Stabilizing the Codebase
When I inherited the project, the codebase needed help. It had switched hands several times: features had been added without documentation and the Git repo was not being maintained. It was clear that I needed to stabilize things and get a clear understanding of how the site worked.
After a couple months, I had the site in much better working order with an up to date Git repo, commented code and a good understanding of how the site was put together. This foundational work helped solve a lot of issues that came up later.