For the few medium format cameras can be bought still affordable is the Diana F + currently the benchmark for the beginner.
Is little that is so easy to extend and with such a good accessory availability. eg Instax or 35mm film replacement parts.
On the camera can be set with some really _everything_ accessories, who wants Tinker has the optimum modular basis.
However, in the long run no substitute for a quality (but usually difficult to obtain) medium format camera system.
Depending on use, you should, if necessary, drag a Holga considered.