How long does it take for gangrene to go from dry to wet to septic shock to death?

Maybe never: Sometimes, what is considered "dry" gangrene (thinkong about tje toes in particular) can be like that for years. Sometimes it can get worse, and that period of time would typically be over days to weeks. If worsening blood supply happens, it could happen faster. Consider a consultation with a vascular surrgeon if this in in tje feet. Hope this helps!

There is no set time: ...& can vary from hours to never. Gangrenous tissue should be surgically removed as soon as it is medically safe to do so(i.e., when anesthesia, if needed, can be tolerated) and something can be done to protect the raw tissue that's left behind- unless infection has already started in which case it's even more urgent and no longer as important to worry about covering the raw tissue right away.