I have two machines... a Knitking standard gauge and a Brother bulky. At one point, I owned 5 machines, one was the top of the line PASSAP that knit 4 colors in the same row. Both of my current machines are electronic with the capability of attaching to my knitting software on the computer, although I don't do that anymore. I know you don't want to spend much money, but the machine manufacturers are few and far between, so even the used machines are a premium price. Don't waste your money on the very simple 'hobby' machines as they are difficult to work. You might just as well knit by hand rather than one of those. Try ravelry.com and knittingparadise.com as they have forums there about machines and some for sale.
Some of my machine creations:
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