Are you asking about a used MF system for about $250? In my opion the best system for this price range would be the Mamiya M645 system with a M645 1000S. Awesome camera with great optics! Very well built.
Helping to save analog photography one exposure at a time
I offer a choice for MF. Ifyou like 6x6, then I have a DuaflexII ihat is a very light weight, fairly compact TLR with decent optics(f8/72mm Kodar). However, if 6x9 floats yer boat, step right up to my Kodak Tourist II. Its a folder, but accurate shutter and clean optics (f6.3/105mm Kodak Anaston)insures super sharp negatives (8 on a roll of 120), and only slightly heavier than the Duaflex. Either camera would be more than adequate for entry level through advanced levels of photography.
It seems that these last couple of posts have a common thread. I believe we are all telling you that you dont need to have a super hi-tech camera to take great photos, its all about you, and what you decide to show the rest of us(your vision). There are no magic bullets, only good basic sound skills.
What is a master but a master student? And if that's true, then there's a responsibility on you to keep getting better and to explore avenues of your profession.
My 6x9 Kodak Junior is superb - and it cost me much less than $250. Of course it's a folder so no range of lenses, but works great for my landscape and architectural photography that I want to produce a little differently than my usual work.
Mamiya TLR, C3 or C220 or maybe even a 330, with one or two lenses. Or one of the many 645 system cameras. Or Bronica SLRs. Rolleicord or old Automat, Yashicamat, Minolta Autocord if you don't need interchangeable lenses. A high-quality folding camera with a rangefinder, possibly, but you're then dealing with possible bellows issues and fairly slow handling.
If you're moving to medium format specifically for image quality and want faster handling than your 2x3 Graflex, I wouldn't recommend using an antique or any of the box or toy cameras. Not that they're not great--I own several and shot many of my favorite images with a few-but they're not going to be the same as a camera that offers relatively fast, precise, and reliable focus and exposure controls.