The outer planets are the honest test of what a telescope cannot do. They are visible, they are findable, and what they show is far less than a beginner expects, which is worth knowing before rather than after the purchase.
Neptune, which is a blue dot
Neptune is about magnitude eight, which means it is easily bright enough for any telescope in this index to show and for good binoculars to reach. What it shows is a very small blue-grey disc, barely distinguishable from a star, and you confirm it by its colour and by the fact that it does not twinkle. At 150x in a 130mm instrument it is a definite disc rather than a point. That is the whole observation and it is still worth making.
Uranus, slightly easier
Uranus is brighter at about magnitude six, and under a genuinely dark sky it is at the edge of naked eye visibility. In a telescope it shows a small pale green disc, noticeably non-stellar at moderate magnification. Neither planet shows surface detail in any amateur instrument, because there is very little contrast in their atmospheres to show.
Finding them at all is the actual work
Both are faint enough and slow enough that the difficulty is identification rather than visibility. A star chart or a planetarium app for the current date is essential, and a computerised mount removes the problem entirely, which is one of the better arguments for one.
Questions people ask about telescope
Can you see Neptune with a telescope?
Yes, in any telescope in this index. It appears as a very small blue-grey disc at moderate magnification, not as a point and not as anything more.
What does Venus look like through a telescope?
A bright featureless crescent or gibbous disc. All the interest is in the phase, which changes noticeably over weeks.
Do I need a big telescope for the outer planets?
No. A modest aperture reaches both Uranus and Neptune easily. What you need is a chart to identify them, because they look almost exactly like stars until you magnify them.