Your question is a bit light on specifics regarding your usage.
Assuming Win11:
4GB: Even a light apps user is running low on RAM most of the time, and/or performance is being affected at least some of the time as a result of the lack of RAM.
8GB: My minimum recommendation these days regardless of use; currently it should leave about 4GB RAM available for userville apps. It hugely depends what you’re doing with that space as to whether you might need more at this point in time.
16GB: Ignoring the current RAM price situation, I normally would have suggested this amount to most of my customers based on the idea that they probably won’t need to upgrade RAM again throughout the life (say 10-15 years) of the PC I’m building for them.
Until 2023 I had 12GB RAM and never ran into any low RAM issues. Horses for courses. For my zen4 build I went with 32GB RAM because the general word at the time was that games would not likely need any more than that for some time.