Thanks for the replies, that was very useful.
I think main upgrades are RAM, GPU and PSU at the moment, so i'm leaving the SSD behind for now.
Here is what i found on amazon
GPU: GTX 750ti 2GB Palit Edition (300W usage)
RAM: 2 x 4 GB HyperX Fury 1866Mhz
PSU: Corsair VS550 550W
All of them for 250 euros. What do you think? Is this a good upgrade? I think all pieces should be compatible with my setup.