I've noticed that Grand Fantasia's programming has some minor errors (memory leak issues) that can really cause lag.
Some tips to reduce lagging.
1. Make sure your computer and all drivers are up to date. This can be modified by the Action Center (for Vista and 7 users). You can set your laptop to automatically update as well, just in case you forget to do so.
2. Make sure Grand Fantasia is allowed through your firewall and antivirus. Speaking of antivirus, you should have at least one installed AV that scans once a week, minimally.
3. Make sure that there are no extra processes/services. These include unnecessary programs. It's best to run just GF. Chrome is known to cause lag to GF. The client also memory leaks, so be sure to shut down your client every now and again. Program to shut off necessary processes
. Clear your cache as well, and often. Delete unnecessary files. Defragging usually does the trick (again once every week or every other depending on use) and getting a program like Ccleaner
4. Lower your graphics/glow effects/etc. Sometimes, that's all it takes.
5. Shut down skype/pando media booster/akami. These are all known bandwith nommers. Be sure to have them shut off before playing. It'll save you some time and headaches.
I hope this helps your lag issues.