One of the first things I did when I got my early-2011 13" MBP was upgrade the RAM to 8GB. Looking back, I can say this upgrade was absolutely essential. Running photoshop was unbearable when I had 4GB. I also noticed that RAM usage seemed to jump up as soon as the Lion OS came out. With my hard drive's life beginning to diminish my next plan is to replace the optical drive with this OWC data double, which will allow me to install two internal HDs. This way I can install my OS and frequently used applications on an SSD while using 1TB HDD as a scratch disk and general storage.
I bought my first MBP a couple years ago and bought the Mid 2012 brand new - mainly because I could add my own RAM and SSD.
Like /u/PrecisionHat suggested, add in an extra HDD in place of the optical drive and get an SSD for your primary drive.
I got this for the extra drive:
Enclosure: https://smile.amazon.com/gp/product/B00724W0N2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
SSHD: https://smile.amazon.com/gp/product/B00B99JUBQ/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1
Wel, I like the DVD drive bay on my macbook anyway: It's how I fit an extra SSD in there...
this! install all apps and the os on the SSD. music, movies, documents can all sit on the HDD in the optical bay. Only reason i have a 500gb is b/c i have windows on there too. while you're at it grab one of these and you have an optical drive for any cds
The Data Doubler is the name OWC gave to its product to allow you to put a hard drive or ssd into the optical bay. It is just a piece of plastic that holds the drive in place.
It is not optimal for a spinning hard drive to be in the data doubler chassis, as it is not really designed to keep the spinning drive stable. It is really meant for SSDs.
You can find cheaper versions of this around amazon and ebay, and even get an external enclosure for your optical drive, turning it into a USB super drive, but the OWC version has the best ratings.
If you are going to do only 1 SSD, put it in the data doubler. If you are going to do two SSDs, then put an SSD in both places, and possibly even RAID them together so that you get a single drive with increased performance, BUT MAKE SURE TO BACK UP YOUR DATA!
Let me know if you have more questions.
Edit: This is the one I bought: http://www.amazon.com/Drive-Unibody-MacBook-SuperDrive-Replacement/dp/B0058AH2US/ref=sr_1_3?ie=UTF8&qid=1457537224&sr=8-3&keywords=data+doubler It is better for holding the spinning standard HDD since it is a bit stronger than plastic, and holds the drive in with four screws.
Easy as can be. OWC is highly recommended.