Best software for intermediate Arduino Diagrams?
No problem sir. 🙂
You can always create and simulate the Arduino circuits for free in www.tinkercad.com
I use KiCad. It is reasonably simple compared to Eagle but still allows you to accomplish a lot. It is Open Source and free. KiCad allows you to create schematics and also printed circuit boards.
If later you feel you need more capability you can use Eagle (an Autodesk product) which also has a free edition that has a few limitations attached none which should effect a starting hobbyist. I like having Eagle installed on my computer simply to use as a viewer for Eagle files I encounter.