A Pentax 6x7 sounds like a good camera to pick up early on...
What really got me into this line of thinking... I'm shooting 4x5 mostly now. And I enjoy printing from 4x5 negatives. Earlier this summer I shot some 35mm and some 6x9 as a diversion (and to check my commitment to 4x5).
I didn't find out what I expected. I found I can take pretty decent pictures with anything. I thought I was going to discover 4x5 was really special and everything else was rot.
Now I still like the 4x5 prints better, and plan to go forward with that. But the earlier negatives still make me happy too. I'm relieved that I don't have to renounce my earlier work.
But instead of locking down the enlarger, now I find myself doing a bit more juggling in the darkroom as I switch lenses and negative carriers.