Things that proved useful in my edc:
- some kind of OTC painkiller like ibuprofen or paracetamol
- a light foldable shopping bag in case you need to carry more. These can be clipped to the outside or your bag or stored in your pants pockets.
- Water. Don't really see that as an option with this bag though.
For the knife also consider a fixed blade without handlescales. These can be more versatile and thinner than folding knifes. Check your local laws before buying anything.
Notebook wise I carry a moleskine A6 and a pilot g2 pen, its nothing fancy but works for me.
Edit: Can't believe I forgot this: Flashlight! Probably the most used item of them all.
