How to mount a floating shelf on ridged ceramic tile
Since floating shelves apply a lot of torque to their mounts, I don't recommend adhesives. That's a recipe for a noisy disaster. 

You can drill tile like that with a few precautions. 


It can be very difficult to accurately start a hole. A small chip in the glaze made with a nail set and light taps can help. Otherwise, brace the drill well against the wall to keep it stationary. 
Don't use the hammer setting. Use a grinding bit (diamond or tungsten) at fairly high speed and with light force. 
Keep the bit aligned during the entire process. Allowing the drill to cant to the side will cause binding, which could damage the tile. 


A stable, light touch should get you good results. If you don't have any spare tile in case the unthinkable occurs, reconsider the value of your fancy shelves. Maybe use a standing unit instead.