This might be a controversial topic with very different opinions, but what are some tips and trick for people who write code in a work setting, but are not trained software professionals?

To give an example: I wrote a lot of automation for a bunch of analysis that run on a daily/weekly basis. I always try to do as much as possible in our data warehouse, but some things just cannot be done there, so I had to resort to excel until now. This requirement has changed now. I do not have deep domain knowledge, but I have a pretty good idea what the things I implemented are doing, so that is not a problem.

My goal over the next couple of weeks is to rewrite most of my automation without excel. I have access to a C# compiler (Shipped with windows - up to C# 5.0 ), PowerShell, can probably get some form of local version control from IT and have access to VS Code. I was trying to plan out how to best do it.

What are some things you guys have learned over the years? What are the gotchas?

Edit: I do program a lot in my spare time, so I am not starting from scratch, but I do not come from a CS background.