Sketchbooks: Strathmore is my go to sketchbook. I try to stock up on them when they are on sale at Michael's. I just recently tried the Strathmore mixed media visual journal for my watercolors, and I love it. I also use Master's Touch sketch paper for drawing and Canson Mix Media for painting with watercolor or gouache.
Pens & Markers: Fabre Castell Pitt pens are my favorite. They are waterproof so they are perfect if you will be using paint or markers. I also use a Sharpie marker and Pentel brush pen with my hand lettering. For markers I use Pentel color pens. They are wonderful and have a HUGE variety of colors.
Pencils: I like an inexpensive mechanical pencil (I think from Target) for sketching. The colored pencils by Pentel are definitely a good fit for my collection of supplies. I love the range of colors offered. Also, I have to hide them from my boys.
Paints: The Winsor Newton pocket box is what I'm using right now for the majority of my watercolors. I chose Reeves to try gouache for the first time. The set was affordable and offered a fun collection of colors. My acrylic paints are for the most part an inexpensive collection of my favorite colors.
I also have an FAQ here for other questions you might have.
I hope this is helpful for any of you who are interested. Remember, whether you have a Sharpie pen and a cheap sketchbook or fine art pens and paper, the main thing is that you are taking time create. Also, it's okay to buy cheap supplies. The first watercolor set I started really experimenting with was $8. I bought it because I liked the colors. It got me interested in trying a new medium and allowed me to get my feet, or should I say brushes, wet.
"You can't use up creativity. The more the you use, the more you have." -Maya Angelou