question: "can i overclock my i5 450M "
Answer : No you may not it is not a K processor (unlocked permitting overclocking
Question: "what do you think i should upgrade mu cpu or my gpu"
Answers:
1. the i5-450M is a PGA988 socket and that is normally a Laptop cpu, so the answer is: Likely you cannot change it, (yes there are exceptions)
2. if you are indeed running a Laptop, what is the make and model of your computer?
Some permit to change the video card, the laptops in those cases sometimes have a selection of 2-3 video cards you can put into the system as straight plug in swap out.