How into this will you get? If you just want to make your own a small telescope is easiest (see the other reply). As things get large expenses go up. Commercial lens are cheap for smaller telescopes, but as you get to large that becomes the cost and so making your own is the only way you can afford it. If you want a large telescope you should again start making a small one, but this time making your own lens - even though it isn't cost effective to make your own lens (vs buy), the experience means you have a chance to make a larger one (and finish, most people who set out to make one large telescope never finish, those set out to make a small and then a large are more likely to finish both).

If you just want to see the stars, goodwill often has telescopes cheap. A refactor can see more than your eye. (or even the binoculars you likely already have!). And the bigger reflectors are seen once in a while.