Well, there are a number of ways to go about it. Plywood with glass/acrylic windows or all acrylic. Or even all glass if you want. Another option would just build a stand and canopy for an exsiting tank.
A plywood tank isn't going to be as nice, but usually used for really big tanks. An all acrylic tank would be nice and you can go from like 1gal to however many gallons. A bit trickier to work with because you gotta use special glue and stuff not normal silicone.
All glass is probably the easiest. Silicone bonds to it, you can get glass fairly cheap compared to acrylic (plexi) and its probably just the easiest.
May cost more to build your own but gives you a good satisfaction. Personally i'd go with a glass tank and a really nice stand and canopy.