Should i Buy SSD first or RAM for my Macbook? I have a macbook pro 15 inch mid 2010.
For school i have to use mostly Adobe applications but they take so long to boot up. 
Not only these programs but other programs too.
What should i do to improve my macbook.
I was thinking to upgrade my ram from 4GB to 8GB.
I was also thinking to buy a Samsung Evo 840 128GB SSD.
But i don't know which one should i buy first.

Which one should i buy first? (SSD or Ram?)
Don't get a 128GB SSD. You don't want to run a 3rd party SSD on OS X without a decent amount of free space since you won't have TRIM support.

Does Activity Monitor show memory pressure? If not, I'd save my pennies until I could afford a 256GB or 512GB SSD. I've done both RAM and SSD upgrades many times and an SSD has always been by far the best upgrade in changing the "feel" of the computer.