There are some simple things you can try to reduce lag on your end, since doing anything about lag on SE's end will take time if they even do something about it (because time and money).

- Turn graphics settings to Standard
- Go to Character Config -> Control Settings -> Character -> set Battle Effect Settings for Party to Show Limited or Show None
- Shut down any teamspeak software
- Shut down BitTorrent
- Close your Internet browser
- Turn off any streaming services
- Shut down iTunes

After that, or if you've already done all of that, you can try more extreme measures (such as subscribing to a VPN, setting up a VLAN for yourself in your own home, paying for faster Internet, etc.), but those are beyond SE's recommended requirements for the game and shouldn't be done if you don't want to.