Nami is a good support.
My issue, .. and probably everyone's issue, .. with playing support is that it is incredibly difficult to carry a match as a support. You get pretty much no gold and you have to share exp with your bottom lane carry.
If they don't do well, .. there is pretty much nothing you can do.
When I play support, I like to play champions who have the ability to carry as well.
My go-to support is Bard. He has good sustain with his heal and his chimes give him bonus exp, mana sustain, great roaming potential, and the bonus damage and passive effects from his meeps will make him almost always relevant late game, even on a support's budget. He basically becomes a cheap off-carry. The problem is, .. it gets easy to get distracted by the drive to collect chimes. You need to have a decent understanding of macro game to be good at playing roaming supports, and that is something that often takes players a long time to understand, .. if they ever really do.