Glass marble mosiac advice? I don't know what to use?

Sorry for the terrible wording!

I have an old glass top patio table that is quite an eyesore. I wanted to paint the base black and glue some of those flat marbles onto the top of it. But I would still like to be able to set drinks down on it without them falling over.

What would I use to glue the marbles down since it is a very large area and its going to be exposed to the elements?

Also is there anything clear I can slather onto it or pour over it after I get all the marbles in place to make it a smoother surface?

I would like to keep it clear so that the light can shine through it…

but do you think if I glued the marbles down and then grouted over them that the marble would still be clear all the way through to the bottom (like little windows)?

And can I even use grout around the marbles over the glass table top??