for being your first tank i would go with glass, acrylic can be tricky, you have to have a smooth cut and the acrylic sement can be messy. 1/4 for either glass or acrylic should be fine. is this for display tank or sump?
My acrylic 30 Gal. uses 1/4th acrylic and it's got some nasty deflection across the front. I would go thicker.
you can find all this information on youtube.com just type in "how to build a fish tank" or "diy fish tank"display were did you learn from video or weebsite?
if either could you tell me the site?
I would go with glass for your first build all you have to do is get the size rims you need and then go to any glass/mirror store and tell them what the sizes of glass you need and they will cut it for you and then stop by a home improvement store on the drive home and pick up a tube of sylicone I (clear) an assemble the peices of glass just like any other fish tank and run a bead of sylicone in each angle and use your finger to smooth the bead out and let it dry overnight before you fill with water and thats it.
PetCo or PetSmart have their tanks (up to 55 gal) on sale right now for $1 gal. So for $30 you can get a 30 gal professionally built tank. 30 gal is a lot of water to get on the floor.
you can find all this information on youtube.com just type in "how to build a fish tank" or "diy fish tank"