VirtualBox Windows 7 speed is slow

Running a Windows 7 64-bit VM on a macOS Sierra host. I installed the VM to do a lot of Windows programming and development, therefore speed is rather important. Right now the VM is running painfully slow. It's very choppy and lags a lot. Any advice to run a speedy VM? (I already enabled 3D acceleration and maxed out the video memory to 256 MB.) Thanks