When it comes to laptops, it has been my experience that a memory upgrade usually makes a noticeable difference in performance and upgrading your processor is not usually a good/viable financial decision. The third option is becoming more and affordable and that is upgrading your hard drive to a solid state drive.
Without going into technical detail, the reason this upgrade makes such a noticeable performance increase for your computer is because a solid state drive is roughly similar to a large flash media card (like you use in your phone or camera). The hard drive does not have to search to find bits of your program or file here and there on a one of a number of spinning disks and then put it together for you to use/view. The short version, it is just faster...NOTICEABLY faster. Perhaps the biggest speed increase you will notice is in how long it takes your computer to boot. Since upgrading my Dell laptop, I have seen a 75% faster boot time. I upgraded a MacBook Pro recently and their boot time increased by more than 50%.
The main drawback to this upgrade has been the cost of SSDs (solid state drives). Because of the price, an upgrade usually means going to a smaller disk size and using more online storage, but as always happens with technology, prices are coming down. This SanDisk SSD is 480GB (almost half a terabyte) which should be large enough for most home use. The drive is normally $150 but is marked down to $110 until April 21st.
Upgrading to a SSD made more of a performance improvement on my laptop than any other upgrade I have done and I recommend it to everybody. Upgrading a hard drive like this means your current drive needs to be cloned (copied exactly) from your old drive to the new one. It is not too complicated, but More Tech Savvy would be glad to help you with the process if you look at it and decide it's a bit more than you want to tackle. You can contact me here.
In either case, I'm available if you'd like to discuss if this upgrade would be a good idea for you. This drive is on sale for through April 21.