Since I usually try to sketch in a coffee shop before work, here is my travel set up:
Sailor Fude de mannen pen, bread and butter pen here. $15. Bent nip allows various line weights by tipping the pen, or very sharp lines by flipping the nib. I think there is a term for this, but I mean writng with the tines facing the opposite way.
Mnemosyne pad from maruman. Super smooth paper. I use dip pens on it, but the paper easily gets soggy if too much ink is used with a dip or brush pen. Can hold up to those as well if your careful. I just love the smooth feal of pulling a fountain pen across this paper. And they have spirals in two sizes I use a lot. The A5 and A5 with no lines or dots.
Platinum Carbon black ink (I keep the bottle in its box in my bag). What I was told from my manga teacher in Japan, "Platinum used to only make Carbon ink in cartridges. But manga artists loved the ink so they were constantly emptying cartridges into a bottles to use with a converter. So now Platinum bottles Carbon Ink." It is a dark strong ink that I love. I also use a sailor black as well at times that is almost as good.
Uni Kuru Toga pencil. I do not recommend this pencil for drawing. It turns the led after each push. But for drawing, I usually do not push hard enough to turn the lead, and also I like when the led gets a big flat spot I can use for wider lines. But it is super fun to watch the gears turn as you write and I needed a 0.3 pencil to force myself to lighten my push and grip. The main reason I started using a fountain pen :-)
Pilot Futayaku(?) brush pen. Recommended to me by Matthew Southworth, comic artist for comics like STUMPTOWN (oni press). Very cheap pen, but hard to find in the states. I don't use brush pens much, but works great for me for learning. Two size tips helps as well.
Pilot Leather 3 pen holder. This was around $20 I think? The Sailor is a long pen (about 16cm) and just fits. And the fat white out pen I am using now fits as well. I have a good luck charm from Samukawa Shrine my wife got for me. It is to help creativeness. And a few business cards and a small sticky note pad.
And other stuff. Eraser guard, ruler I trimmed the end off so it fit in the pencil case. Pencil case that unzips and works as a pencil stand. OH, the lead holder is huge. I have two, a big fatty and a slimmer one. Makes gesture sketches stay gestures before going in with the smaller pencil.
Cheers and ink on!!
EDIT: Started on phone, came back on PC to add details