This is another quite subjective topic amongst fountain pen users but generally just be sure to use high quality , non-coated paper.  Low quality paper tends to collect on the tip of the nib when writing causing ink to bleed and your lines to skip.  When possible choose quality paper with a high cotton content to get the most out of your fountain pen when writing.

Note: Writing on recycled types of paper with most fountain pens and inks usually yields subpar results.