You're looking at around 150-250 fps depending on the settings that you chose to play with, and that includes the resolution and framerate of your monitor as both of those things will change how graphics intensive a game is to run. 150 fps for better looking 250 for low settings, according to users with a similar setup in another forum. Now, as for Just Cause 3 there really isn't anyone who is going to be able to give you any answer that will be relevant to you. The game seems to be too unstable for people with even the newer 980ti to get stable framerates regardless of the settings, the game is just too poorly optimized. A comparable game like GTA V could be used if you'd like to know what framerates to expect and most users seems to be getting a steady 60fps on the 750ti when using medium settings. You could probably expect to see 80-90 fps is you were to run the game on low.
On another note, after looking at your build I have a couple of recommendations to offer. If you intend to use this system for mainly gaming, I'd nix the 1TB drive and settle for a 500GB (if the difference in price is substantial) and put the money towards a better graphics card. The same can also be said for the optical drive if you dont intend to use one. I haven't had on for the longest time and thanks to Steam and digital game copies I haven't missed it either. And lastly, I'd swap the RAM that you've chosen for the Corsair Vengeance option. It's the same speed and $7 cheaper. I know that it sounds like nickel and diming everything but when it comes to building a budget system it's the only way to get ahead.