Become a mentor!
Since I've become a mentor I feel it's actually added more to the game for me, but I enjoy helping people. I frequently walk by newbies and toss them a few thousand gil and a welcome message offering help if they ever need it. I've done countless Limit Breaks and Missions for new players, and it doesn't really get old.
Of course, there's the occasional question I have no clue how to answer, but having a lot of friends on the server means I can just direct them to someone or even somewhere that I know they'll get the help they need. There's quite a few people I've built relationships with and have been friends with for years now (even outside of FFXI after they stop playing or something).
I recommend it to anyone who likes to lend a hand. Very rewarding and "adds content" in a sense.