Low FPS in game. Rate my comp specs and tell me what I need to upgrade. Tech pro pls

[Princey]

I'm not good with computers, I'm horrible at this whole tech-y thing, and I know FF is very graphically demanding. I'd like to play FF with the best graphics possible but currently I'm at 15-30 FPS since I started. (Lowest for crowded cities/sanctuaries/fates). I want a computer that can run FF well. It's about time I upgraded my computer anyways.

Windows 7 32 Bit
Pentium(R) Dual-Core CPU E5300 @ 2.60GHz
Video: Nvida GeForce 9800 GT
RAM: 4GB, 2 sticks of 2GB, 3.50 at max. Though I don't think I'm running on 3.50 GB ram. Does RAM get depleted over time? My comp seems slower lately.
Motherboard: Asus P5KPL SE

While I run final fantasy, I open up task manager and go to performance, the "CPU usage" meter isn't very high, it's pretty normal, sometimes spiking up to 80-90% but it mostly stays on 50%, Same thing for the "memory" meter, it rises up while running final fantasy, leaving only 1.3GB of memory usage left. Tho for some reason when I ran the benchmark thing and checked the cpu usage it was like at the limit.

Idk what's going on with my computer but some insight would be nice so I could forward it to the tech place, most likely gonna have to buy a lot of new parts. This comp is about 4 years old (2009). And I don't think JUST buying a new video card, the one recommended on the FF page will help.

Money isn't a problem but I don't think I'm gonna spend a lot on state of the end parts JUST for FF, when I can run games that I usually play a lot like League of Legends on 60 fps perfectly fine.