I have 64-bit system, do you suggest me to buy horizon or not? Just a final question, to start with ED wich controller do you suggest to me? Is it fine to start with a standard joystick like the microsoft's one for xbox and pc or should I directly take a hotas joystick?
I'd take it slow. Elite is a money pit.

From your specs, I think you have a laptop, right? I think you should start with KB+mouse (perfectly playable, one of the best PvP players I know play on KB+mouse) or if you have an XBox controller, you can use that.
As for whether to buy Horizons, I'm not sure. It won't be completely comfortable playing unless you crank the resolution down, I think. I have one laptop I use for playing when I travel. It's a similar i5 and GT920M, which is tad better, but on planets and with low details, FPS still fall under 20, sometimes, while in space it's a perfect 60FPS.
I think I'd wait and play the base game. If you fall for Elite, like we did, it will eventually convince you to buy Horizons, HOTAS, new computer, VR set,...
