Mouse lagging on iMac I'm using iMac 21,5.

Since my magic mouse broke, the new one wasn't working properly, it had insane lags, I bought another wireless gaming mouse and it works better but still have lag issues.

I was checking Bluetooth/Mouse settings and it says:

"Keyboard connected.

Mouse not connected."

Pressing mouse to connect, doesn't do anything. 

Maybe the problem is there. Please help me.
I was having similar trouble with a Logitech bluetooth keyboard and mouse, when I plugged the transponder dongle into the USB port on the back of my iMac.  Researching the issue, I found several people suggesting to move the USB dongle away from any USB 3.0 ports, and as an EE I figured it also wouldn't hurt to get it closer to the devices it's talking to.  So this is my setup now and I've been a happy camper ever since I bought a USB 2.0 hub, plugged the dongle into that, and moved it near my keyboard and mouse.  (Of course the hub is connected to the iMac in the back -- should be obvious, but just sayin.)