KitKatnip, I completely understand your frustration with the gil seller spam! Here's what I did:

I made a new tab in the chat box, and set it to show Tells only on that tab, and I turned off the sound notification for Tells. I check the new tab every once in a while in case I missed someone who isn't a gil seller trying to chat with me. At least I don't have to hear the notifications and look at all that pink text this way, because I find all of that really distracting!

This works for me because I'm generally a solo player so I'm not expecting to hear from anyone anyway. YMMV. :-)