>>3795198Always worth wasting a potential frame and making sure the film catches before closing the back than doing what you wound up doing...for future reference.
>>3795267YEP
>>3795351I'm in the 'learn your gear really well' camp. I went a few years with just my Bronica and 80mm before buying another lens. Square format is a weird beast and if you're still new to it, I'd stick with the 80mm for another 6-12 months to get a real feel for the format and gear you already have.
After some more time, it should be pretty obvious which focal length you should go for next. There aren't that many focal lengths in the system. If I were you, I'd decide between a 50mm or 150mm. You could also just get both, as neither lens should cost you more than $150ish.
In terms of what I find useful, I'd say 80mm > 50mm > 150mm. However, I find the 150mm most enjoyable to use when the right situations call for it.