Your Processor and Graphics cards are very weak in today's standard. You have a 1st Genration Intel Core series (Nehalem architecture) Processor which has reached its End of life long back and you won't be able find any Processor to be fitted in that motherboard. So unless you change the whole motherboard+processor, CPU upgrade path is closed.
Now, regarding Graphics card, at what resolution you are gonna play the games and how much you can spend? My suggestion will be a His R7 250 1GB GDDR5 @ 6.5K and a goofd PSU like Antec VP450 @ 2.6K. Anything more powerful thamn that, will be bottlenecked by the CPU.