About my pc... I need help !

So the thing i need help with is that im not to good with pc's and what you can put in what. Like because of all the ddr1 ddr 2 ddr 3 so on...
Long story short what processor would i be able to put in my pc?

My current spec's are:
Intel core i5 -2300 2.80GHz
nvidia geforce 750ti - 4GB
8gb ddr 3
fuck knows what motherboard all i know its analienware what is about 5 or 6 years old.



So i wanted to upgrade my cpu but not sure what to get or what will fit in? Also any pointers on fixing this or maybe get some parts cheaper for this pc it lags quite a bit on games. Not all the time tho?

Thanks in advanced for anyone that helps and give's me pointers.