To run League of Legends on dedicated server with GPU 3D acceleration you need to do flowing actions:
1) Dedicated server which has GPU, server description should contain "int. GPU", "on-board GPU" or add-on GPU with model specified.
2) Choose to install Windows Operating system (Windows Server 2008/2012/2016)
3) Login using Remote Desktop client (mstsc.exe)
4) Install VNC server. For example TightVNC, also it can be other VNC server type.
5) Login using VNC viewer. There you should see Windows Lockscreen, use VNC viewer top menu button "Send CTRL+ATL+DEL", and now, type Dedicated Server credentials to login.
6) At this point you should be able to change screen resolution, this feature indicates, that server GPU is working.
7) Download and install League of Legends game client and bot software.
8) (Optional) Update graphics drivers