Well, just because it is the same socket doesn't mean it will be compatible. Check your laptop manufacturer's website for information on what CPUs that laptop might be able to get. Make sure you update the laptop's BIOS before attempting to upgrade the CPU.
Honestly, you will see some difference but it won't be night and day. In my personal opinion, you are better off saving your money for a better laptop. In another year or two, a cheap laptop will be very noticeably more powerful than yours. Actually, I think cheap i3 laptops are definitely more powerful.
OK thanks, I will wait and save enough money to buy a better laptop.