Relatively inexpensive, good for learning on but also useful for most beginner-to-intermediate level projects, so I don't need to buy another one for a few years.
So you want one of these new or still in the oven rigol/siglent 12-bit things. Just stretch your budget some 25% more to get it done right. I mean, if you are thinking about interfacing a microcontroller and a LCD screen, or something as basic as that, four channels are useful.
Even one of these will not be the same than a pro oscilloscope in the thousands range, but any less than that, and you will fail your target.
Buying an old, 8-bit, 4-channel old entry-level rigol/siglent devices isn't the way to go, at least while people continue to ask for about 300 bucks.
Of course, you could go the very wrong way, and buy first a toyscope Zeeweii 2512. Then one of those Hanteks that many (most?) buyers are abhorrent at. Then you finally could get a decent 400 bucks benchtop scope and realize you wasted half that money buying crap.
But in the meantime you could easily fool yourself into thinking you got for pennies something that performs better than some other thing that cost three or four times that money. You'll only need to believe the published cheap toyscope specs are like the Bible (and some stubbornness, too) to achieve that.
If budget is really tight, it would be wise to follow tggzzz's advice and to buy something that does fewer things but does it right. At least it will continue to be useful in the future and you won't think about throwing it in the trash bin.