Best products from r/Gouache

I had this same question a few months back. Ive found that any paper with higer gsm is better and 100% cotton is also a major plus. My current top 3:

• After suggestions I received from here, I tested out the Stillman & Birn Nova Series which I ended up really liking but I didn't love it. It got the job done, the toned paper was a nice effect, but I felt like it made my gouache works look more like watercolor paintings - Specifically, I think the paper it was too absorbent for gouache (made my washes look thin and translucent even though I use M.Graham and Windsor Newton and Holbein) and it had slight buckling. But id still suggest it because it's very different from other books, it lays flat because the pages are sewn and it is highly durable - I thought id destroy mine but it held up very well. I even used acrylic paint on certain pages and there was no bleeding or weird reactions.
  
• I just recently bought the small pocket-sized version of the Moleskine Watercolor sketchbook. I love the style and look of the sketchbook, its very trendy. The size is nice. However, the quality of the paper is okay. Id rates it about 7/10 because of the thickness and texture. It can sometimes feel very thin when I'm working with a lot of layers but I believe it because it is made for light watercolor washes, its its only 200 gsm. I've found that it doesn't do well with repeated strokes or reactivation of old washes of paint - it can react like its been overworked/look crumbly. Id still recommends you give it a try, everyone should have one Moleskine experience just for the opportunity to try different brands paper.
  
• Cost effective and attractive design. I highly recommend trying the Strathmore Watercolor Art Journal. I have this journal, I bought it from my local Michaels Arts & Crafts supply store. It is just as good as the Moleskine if not better because of the unique shape options and price. The only downside to this journal is the softcover - its made of bristol board or some type of thick cardstock type paper. Other than that, I love the way the paper reacts to the gouache. It has minimal warping and does not bleed. It is also 300 gsm which is better.

Moleskins are pretty bad for gouache. Your best bets will be a watercolor paper, minimum 110lb, but you'll get better effects with 140lb paper.

If you like having notebooks instead of loose paper:

Watercolor sketchbook with 110lb cold press paper

Watercolor spiralbound sketchbook with 140lb cold press paper

Strathmore watercolor sketchbook 140 lb cold press paper

I've used mixed media paper for watercolors, but I try to avoid anything less than 100lb cold press for watercolor or gouache, cuz the paper will buckle and won't handle the paint.

I do the same and am a fan of Micron pens.
https://www.amazon.com/dp/B0008G8G8Y/ref=cm_sw_r_cp_apa_i_EZmjDbR5J0EV7