You can buy remarkably cheap reflecting telescopes these days on a mount called the Dobsonian mount. They don't (usually) have fancy GoTo automated pointing and tracking, but give fantastic bang for buck as the majority of their cost is invested into the biggest primary mirror possible.
Building a telescope would be a great hobby and learning experience, and there are many books which will show you how. Just don't expect to save a significant sum of money over a commercially built scope - it could even be more expensive to build your own.
Fancy GoTo tracking mounts are not usually worth the expense and hassle (in setting them up) for a first-timer, though the Orion Intelliscope series is an intriguing compromise. For an extra $100 or so, the telescope has no guiding motors, but tracks where you push the telescope and a hand controller will tell you how much further you have to go till you reach your target.
My recommendation? Get the biggest Dobsonian mount scope you can afford. With a mirror greater than 10" things begin to get large and unwieldy, so 10 inches (mirror diameter, not tube length) is my recommended maximum size for a first telescope. Just go for the biggest aperture you can buy and easily carry. Don't invest much in GoTo systems, as although they can be quite useful they are also a pain to set up if you don't have the scope permanently mounted.