As a starter, I use CleanShot X [1] to take, annotate and share screenshots every day. HazeOver [2] is a nice app to keep you focused by dimming the background of other apps on your desktop. I drop all my links and references into My Mind [3]. It can be easily searched and removes the burden of organising the content upfront.
Disclaimer: I'm crafting Raycast [4] which is a productivity tool for developers.
[1] https://cleanshot.com
[2] https://hazeover.com
[3] https://mymind.com
[4] https://raycast.com