Consider the various aquarium shapes. Tall octagons and hexagons are popular. Cube and cylinder tanks are also available. The standard is a long rectangle, which tends to look bigger than it really is and is therefore a favorite among hobbyists. Choose from plate glass or acrylic materials such as Plexiglas.
Plate glass is heavy.
Plexiglas scratches easily. Most pet stores sell full setups with everything you'll need to get started. If you're serious about your aquarium, you'll be cautious about these deals, since the kit might include things you don't need or brands that are substandard. Consider getting a tank stand if that's appropriate for your space. There's really no best stand.