Maybe watercolors are not your thing. Maybe not even watercolor pencils, that's OK. There are some GREAT markers that will work perfectly in your travel kit.
The thing to remember about markers is that they are a bit more expensive and if you try to use them on an uncoated paper (like a watercolor journal or drawing sketchbook), the ink will be gone in a heartbeat, so make sure you are using a surface compatible with markers - coated at least - specially made marker paper preferred. I'll include a recommendation for marker journals below.
First, my favorite markers.
The best value in markers on the market are the Duel Brush Pens from Tombow. They are are the best because they last (assuming you're not using them on watercolor or other uncoated paper), have a smooth flow of ink, blend colors, and have a great firmness/flexibility balance on the brush tips. They also come in several pre-packaged sets that can match your favorite subjects such as landscapes, flesh-tones, desert plants, etc.
These are by far my favorite marker sketchbooks. I especially like that the pages are perforated so you can tear them out easily and give your art away (or sell it). There is also a loose sheet included in each to keep your ink from bleeding through to the next sheet in the book, which is always a possibility with markers.
I have been art-journaling as a way to pay better attention at conferences, in long group meetings, and in countless hours of waiting while my children were at dance rehearsals, classes, competitions, intensives, and performances. I have a bunch of these in different sizes, weights, and textures. I keep one in my backpack, one in my motorcycle pannier, one in the seat pocket of my pickup - you get the idea.
There is no absolutely "right" solution. However, I like all the products from a company named "Handbook" (or "Hand•Book Journal Co."). I like these because they are both functional and sensual. Functionally, the paper quality is top notch, the journals have a pocket on the inside back cover, bookmark ribbon, and elastic closure (though the elastic closure stretches and wears out quickly). Sensually, they "feel right" in one's hand. The covers are cloth, the weight is substantial without being too heavy, and they hold up well to being tossed around. They also fit in a big coat pocket, the pocket of my utilikilt, and the inside pocket of my vest.
I usually prefer the "Large Landscape" size. Here are a few different options.
I travel a good bit, but you don't have to get on airplanes to find great opportunities to create a quick piece of art.
I like to use watercolors when I'm able because:
They are easy to prep, because there really is no prep other than having some liquid available. Yes, I've been known to use coffee during business conferences if it would have been impolite to get up to get a glass of water.
They are inexpensive, relatively. Watercolor sets are WAY more affordable than acrylic or oil.
Unless you are trying to be photo-realistic, watercolors almost require a sense of playfulness that fits a beginner or amateur well. The media gives you a perfect excuse for not being precision-focused in your explorations.
There is almost no clean-up or mess.
A good set will last you years. The larger set in the featured photo above as been traveling with me for 15 years. I've had to replace a pan or two once in a while, but it's definitely been worth the investment for a semi-premium 24 color "half-pan" set.
The little 12-color set is super easy to take everywhere. I have several of these sets - one in my travel bag, one in my motorcycle pannier, etc.
Recommendations:
For your "Primary" set I recommend a 24 color half-pan set something like what I have in the photo above. I honestly can't find the exact product that I love so much - maybe they don't make them anymore, but look for these elements:
Replaceable/Refillable "Pans" - If you go through your favorite color quickly, or hate a color in the set and want to use a different one, these little modular plastic pans are wonderful. Mine can also be re-arranged to fit my personal preferences - like putting flesh-tones in one area.
Room for a few different-sized brushes.
Plenty of room in the lid or another palette element to create washes and blends. These kits are not designed to give you the volume you'll need for art bigger than about 10x15 inches. Think about the size of paper you can fit in your backpack and these will be fine. For images larger than that, you'll want to buy tubes of watercolor and use a larger pallet such as a dinner plate or ice cube tray.
I like the center area of my larger kit because I was able to add 4 more pans, plus room for some watercolor crayons. If needed, my tray could hold 36 half-pans of paint.
Here are some examples of art using one of these pens.
The examples below use the brush pen for the finishing ink lines. The ink is water based, so you can use it alone and then create washes if you're just wanting to work in shades of gray.
