Great photographs are the result of hard work and an idea, even if a vague one, that can unite many images created over time. One sure way to undercut the unity is to use many different lenses, cameras and films. (How would Avedon's work look if he had shot some 35mm color neg with a fish eye, just for giggles?) It's hard enough to do great work with one camera and one or two lenses and no more than two films (one slow and one fast). Seriously, that's plenty challenging.
If you go that route, suddenly everything starts to have a uniform optical space. (Compare that to your average landscape photographer, with the super wides and the macros jumping back and forth. It's all very unsettling. Very few people can pull it off.) Now, you can choose different lenses for different projects, but try to keep each project so that the same film/camera/lens combos are used for all of the pictures in that project.
Also, shoot more MF. You'll get 15 frames on your Mamiya, so you can finish the roll faster. You'll find that you see better. The bigger negs are so much easier to proof and edit, too.
Hope that helps. Photography is incredibly rewarding but it is not easy.