First of all, install a fresh copy of the latest version of Minecraft.
After that, download and install the latest version of Optifine: you can find it here.
Make sure the version of Optifine matches the version of Minecraft.
Now, to enable the mapping of Realistico 07, you need the latest version of Continuum: you can find it here.
Realistico needs some settings to be displayed correctly. I made a zip with all the files you need: download it here.
You should put these files in their folders after following the screenshots below.
Now, close the game and copy the settings files you can find in the archive and replace the ones in the directories.
I recommend to extract the shader pack in a folder, and rename the text file (containing the settings) using the same name of the folder.
Here's an example of the folder structure:
At this point, the game should look like in the following screenshot.
For reference, I'm using a 4.00 GHz CPU, 16GB of RAM and a GTX 1080 on a 1080p monitor.
I get a consistent 30 FPS in full screen (1920x1080). An SSD is more likely to give you these type of performance.
If you're looking for a fast SSD on a budget, I recommend this one. That's the one I use, and it's amazingly fast.
If you're looking to upgrade your computer, I recommend the following components: CPU, GPU, RAM, SSD.
If you experience any kind of problem, you can fix common issues and read answers to common questions.