What kind of paper would work best?

ink and gouache both are water-based paint so use watercolour paper .

canvas is for oil and acrylics .

Illustration board or watercolor paper would be best for gouache. I'm not sure about the ink on watercolor paper. Smooth Bristol or illustration board might be best for ink.

Ink is kinda' like watercolor, so I'd say you should look for the gsm on the paper. Cartridge paper is about 90gsm. You should go for 120 and above. In the 120 to 180 range, you'll need to stretch your paper to prevent it from buckling. 200gsm and up is usually alright.

For gouache, you'll want tooth. So, I'd say either hot pressed watercolor paper, or canvas.

If you'd like a paper for both, I'd suggest hot pressed watercolor paper of at least 120gsm. When using ink, you'll need to stretch the paper. With gouache, it shouldn't be a problem.

Surface determines what your final painting will look like. Different people have different styles, so naturally they'll like different surfaces. Start off from one kind of surface, then branch out to different brands and kinds of surfaces. I hope you can make a good decision with the information I've given you. Happy painting! :)