The OP really has two questions
1. What is the cheapest rig you'd use
2. What is the smallest aperture
2 is correlated with 1, but not completely, since a 76 pronto will easily cost as much as a ten inch import dob.
What I ask of my rigs is that they do what they are supposed to do. The view should be steady. The focuser should work at all angles of the sky without jiggling the telescope or making it unusable even for a few seconds. If there is a go-to or dsc system, it should perform when asked to. When you point the telescope somewhere, it should stay exactly in the spot where you placed it (not counting the tracking) without jiggles, a lot of play or looseness that causes it to sway away from that spot.
These seem to me fairly simple requirements but in actuality they are very difficult to pull off. If one says, "I like all kinds of restaurants, the cheap dives and the high end five star places overlooking lakes and beaches," that seems simple enough. If you add, "But I don't like eating in restaurants that leave me feeling nauseous," then I think most people would consider that uncontroversial.
But in astronomy a lot of the gear for sale is equivalent to gastronomics that leave one a little bit nauseous. It's just a bunch of stuff that doesn't work, it's designed to be sold, not used. Food that is designed to look good in an advertisement but not actually eaten.
I don't really have much to say about *types* of telescopes but I have a great deal of thoughts about poor quality telescopes. I'd rather watch TV than use a scope on a mount where you have to go 3 degrees past the object you want to look at and hope that when it springs back it will be more or less where you want it to be. I like my gear to be usable. C8 or 81mm apo or C14 or GT130, I can use them all or adapt to any one for long periods.
But there's a lot of bad gear that would drive me away from using it to observe, never mind the aperture or optical type.