hey well ive seen peope playing acoustics with slides and i was wondering what are the best slides to use and do some glass slides work better than others

When you get a slide, make sure that it fits on your finger. This seems like a big "duh" factor, but I've seen plenty of people with a wrong size slide.

Personally, I prefer metal over glass.
I too prefer metal, and I like the feel of brass but check out what works for you - glass was always too loose feeling for me perfonally.
I play with a glass slide. I think metal slides sound too harsh usually.
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I like a bit of brass, I have a glass and a steel slide kicking about though. I'd advise finding one that fits best regardless of the material to begin with and then just expanding your collection from there.

That's how I and many other slide players go about it

just make sure to try all different materials and find which finger you're most comfortable with it on.
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