Sorry to say but if you are asking do not do it.
If you still want to do it start with a smaller tank like 10g to get your feet wet.
Buy acrylic sheets at your local hardware store. HomeDepot, Lowes they all carry them.
Get some good plastic epoxy.
Cut them on a table saw and glue them in place.
I always go over with silicone on all the seams inside for peace of mind.