Apple memory for your memory upgrade

If you ask me between buying a new computer or simply upgrading my current one, the best option for me at the moment especially since I am financially strapped is upgrading.. But since my Apple mac book is getting slower and slower due to my incessant installing of programs in it, I guess it is time to get that additional Apple memory as an upgrade for it. Usually laptop memory is the not the only thing essential to make the laptop run faster but this is one of the main components to consider for upgrade. Looking for the correct memory module for a memory upgrade is easy but I was told to limit my choice to those original apple memory as this is the only thing which runs in mac book properly as through study and careful research..I guess I cannot dispute this fact even though it is more expensive than the generic brand memory.