I would say at least 12.
One for each season, at least.
And at least 4 for different occasions.
One for work, an office scent, something light and airy.
One for elegant occasions, something classy and confident.
One for date nights, something sexy and seductive that drives your partner wild.
One for shopping, going out, lunch dates, etc. At least one, preferably multiple.
And at least 4 for your moods. One for when you’re just feeling spectacular and wanna present yourself as being on top of the world and make sure you rock that fragrance as it’s probably the most important in my opinion. One for just relaxing around the house, reading a book or watching a movie, something comforting to you. One for when your feeling down, it should be a cheerful fragrance, something floral and fruity and fun to get out of your funk because life is too short to be sad so you need a fragrance to help snap you out of it. And one for bed, this is one for me personally. I love a darker oriental, something with an oud or incense or patchouli note to help lull me to sleep.
My opinions on the minimum amount.
I’ve personally over 130 bottles of cologne and my wife has probably 25 bottles. The sense of smell is my favorite sense so it just makes good sense to me that I smell well!