$0 (at first)
Using an astronomical telescope is hard work, and the results are nearly always disappointing. Planets are very small targets, and through a small telescope they look like a little circle. You are lucky to see any detail at all.
First just get used to watching the night sky, learning the constellations and asterisms. Watching the motion of the planets against the stars. See Venus brighten then disappear behind the setting sun, only to re-appear as a morning object. Look for pleasing alignments and syzygy. Visit some dark sky locations and see the milky way. Point a camera at the sky and let it record star trails around Polaris.
Then a pair of binocular or a spotting scope is useful to see some detail on the moon and deeper into star fields. These are general purpose instruments, good for birdwatching as well as stargazing.
Sign up with the Bradford Robotic telescope, then you will have shared use of a 34-inch photographic telescope, in a dark location. You will get better photos of the planet than you could ever hope with backyard equipment.
Join up with a local astronomical society, you will see what is possible with an amateur 'scope.
And when you find this equipment limiting you can look to purchase a decent sized reflector, but by then you will know what you get for your money, and how much you are willing to spend.