There's not much risk if you start small then work your way up to a big tank.
Plywood tanks are the riskiest. Even the best built plywood tanks can end up being leakers. If wood working is a hobby of yours, it might be worth a try. Plywood tanks are labor intensive and will probably take a few weeks to a few months to build.
Acrylic tanks can be the most expensive to build. It takes some experience with acrylic solvent cement to get perfect bubble free seams. You don't need perfect bubble free seams to have a leakproof tank though. I've built 3 acrylic tanks. An acrylic tank can easily be built in one day all by yourself. Knowing how to work with acrylic is indeed a nice skill to have.
Glass tanks can be expensive also. Finding an economical glass dealer can be toughest part. You might find that tanks at glasscages.com are a better value than DIY glass tanks (At my LFS's Great Lakes Aquariums are cheap). If you can find 1/2" glass at a great price and have a helper (for lifting), then maybe this is the way to go.