The importance of paper quality depends on which ink you're using. I like Noodler's Black, because it writes well even on cheap paper. It starts reliably and it doesn't feather (spread horizontally) or bleed through the paper easily. I've tried many other inks, trading samples with other fountain pen users, and I never found anything else so trouble-free.
Ink spread and feathering on cheap paper is unfortunate and frustrating. I would also add pretty much any pigment or iron gall-based ink to your suggestion. Unlike dye-based inks, i.e. the vast majority of your vibrant colors on the market, these contain tiny particles that are (with a little bit of oversimplification) permanently trapped in the cellulose fibers of paper as you write. The end results is that these inks are waterproof and don't show the dreaded feathering/bleeding on cheaper paper. I recommend the Rohrer and Klingner Salix and Scabiosa, two inexpensive iron gall inks (blue-black and purple-gray), Sailor Kiwa Guro and Sei Boku (pigmented black and blue) and the Platinum pigmented inks (available in blue, red and black IIRC). The Salix and Sei Boku have worked wonderfully for me on copier paper with no clogging/cleaning issues so far.
I have a Mont Blanc fountain pen, which I want to use as my main pen but cannot due to the ink spreading and bleeding through cheap notebook paper. Thank you for the ink suggestion.
I should point out that I use a Lamy Safari, which has moderate ink flow. If your Mont Blanc is an exceptionally wet writer, and you don't want to get the nib adjusted, you might want to try Noodler's X Feather, which is a version of Noodler's Black with even lower feathering (at the cost of longer drying time). But I suspect the drying time could be annoying, because Noodler's Black is already somewhat slow drying.