Help me upgrade my PC

[mario7770]

I played ghosts in ultra settings without a single lag but when i play Battlefield 4 it runs smooth for 10 seconds and a huge fps drop.
pls tell me what is my bottleneck here:

CPU: Intel Pentium G3220 3.0Ghz 4th Den
RAM: Gskill ripjaws 4GB 1600 DDR3
Motherboard: Gigabyte G1.Sniper B5
GPU: AMD radeon HD 7770 GHz Edition 1GB
OS: Windows 7 64 bit

I always play games at ultra at resolution 1600 X 900 since its my monitors maximum that can support.I normally like to play games like BF4,COD ghosts etc.
since im in a low budget , pls tell what should i have to upgrade

 

[toyota]

every part of your system is a bottleneck for running demanding games on ultra. you need more ram, faster gpu and at least an i5 cpu.

 

[Shmee]

Toyota is right, plus you should make sure you have an adequate PSU.

I would consider another 4 GB RAM, an upgrade to an i5, and a video card upgrade.

 

[Piotrsama]

Maybe BF is too much for that 7770.

But, before buying anything:
- Update AMD drivers to latest version.
- Reduce image quality and tell us if it improves performance.

Also: Download GPU-Z and monitor GPU clocks when gaming. Check if there's throttling.