Upgrade memory to at least 8GB, Get a SSD and external graphics card like 1060. That will bump it up but I would assume due to the age and restrictions on CPU upgrades with your mobo. You will still have lower FPS. I'd be surprised if those upgrades even get to you to 50fps.
Upgrade CPU if you can but as I stated, due to age of your mobo I'm sure you are restricted to limited upgrade paths in CPU dept. If it can even be upgraded. Which I doubt.
I'd save and just get a new PC that will last into the future. Expect around $1000 even for a new low end budget gaming PC. Unless you buy used somewhere.