Best online mixer?

WATS THE Best free app for mixing music? AND CAN YOU BUY A MIC THATS CHEAP THAT YOU CAN PLUG IN

DJay Pro is actually pretty good. There is a free version but paid is worth the money. I tried it only because it connects with Spotify and other music apps. If you do some research, you may find how others are using in regards to the mic option. For mic it is always best to have it on a small mixer since you will need to connect speakers. It just depends what you are trying to accomplish.