Make sure you have an up-to-date Microsoft .NET Framework and an archive tool like WinRAR or 7-Zip installed.
The of Ragnos (version 3.1 "Legacy Patch") is not just a bug-fix update. It is a manifesto. Here is what you get when you install the latest client:
"I have a Dell Latitude from 2014 with 4GB RAM and Intel HD 4400. I get 35-45 FPS in team fights. The game looks like an animated cartoon, but it's smooth, responsive, and actually fun. This is the only modern competitive game that works on my school laptop."