BEE sketchbooks are my go to they're so nice and you can get them off amazon. The pages are perforated so if you want to frame a drawing you can take it out really easy.
I've tried Illo paper, but its bristol board smooth and for some reason gouache dose not feel right on it to me, and the strathmore 400 and 500 papers are good, but can be a bit pricey.

This strathmore sketchbook dose happen to be on sale rn
https://www.amazon.com/Strathmore-441-7-Wirebound-Watercolor-Journal/dp/B007V5IHBQ/ref=sr\_1\_27?keywords=watercolor+sketchbook&qid=1637204357&qsid=136-1980556-1294864&sr=8-27&sres=B08RJYJ81R%2CB01GTR6GHS%2C8883705629%2CB083QZKGDS%2CB003CTJFDE%2CB018QCQOMG%2CB008HTD0BC%2CB07LDK5HZL%2CB003YIXDKE%2CB07TMYT6LM%2CB08RBZ9NQW%2CB086BQPQQL%2CB07GNXCJHR%2CB08KLBRZGB%2CB08V4QHJWH%2CB09CLM6XN7%2CB08BQXR64P%2CB01NH16E9Z%2CB08NY3T1JZ%2C194757504X&srpt=ART\_MEDIA\_PAPER