Before you go and spend your savings on new computer components, consider getting yourself adequate power supplies and cooling.
Add exception in anti-virus/anti-adware for FFXIV.exe or the FFXIV folder altogether.
Put Windows 7 in performance mode so you're not wasting resources on the actual o/s look and feel.
Update to current graphic adapter driver.
Turn off all background software that you may have running (Skype, utorrent, etc.)

Also try pulling out a stick of ram to see if that is the cause, if you're lagging even more then it means you're in need of more ram.

SSD doesn't affect gameplay at all, it only affects loading time between maps and instances.
SSD won't be able to perform if you lack ram or cpu power as well.

Make sure you have enough power going into your pc, plug directly to the wall outlet rather than going through a power bar (power bar has wattage limitation).
If you don't have enough power, you won't be able to drive any power hungry pc components like cpu and gpu.

Apply new thermal paste every 6 months or so and clean out the dust from your PC as it will cause venting problems.
If your pc isn't venting, then the components would be easily overheat, thus slowing down performance.