Ok ideally with wind noise you would want an Omni mic like the one suggested as t hey handle wind slightly better than the rest of the pickup patterns due to the lack of proximity effect.
Shotguns.... Eh you wont get the best sound unless you invest more money than you are looking to spend I dont think, and especially for group interviews they wont work really well as if someone starts talking in the group and the shotgun is pointed at someone else, you will lose that conversation entirely.
However if you are looking for something to mount on a camera to pick up what your camera is pointed at a shotgun wouldnt be a bad idea.
Unfortunatly it looks like what you are describing are several different situations that would all require different approaches/mics. For your basic tpye of situation with interviews, especially outdoor ones, I might consider the omni reccomended above(There are alternatives, but as I havent heard the one above I cant compare against it) to start with. Then you can start adding mics as budget and means become availiable. Pick up a mic stand for that person that you are interviewing to talk into if you need to, mounting an omni on a camera is going to pcik up that camera VERY well, and what you are shooting not so well.
If you do a LOT of camera shooting a shotgun would be better, though to be honest even in that case I would still try to get the mic away from the camera. There is a reason when dealing with shotguns there is usually a person dedicated to each shotgun, that way they can adjust to keep people on axis as much as possible, they are very sensitive to axis changes.
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