Viva, lisap, jenanded -- It's interesting what a mental hurdle it can be to buy multiple pairs of shoes. Same with outerwear and bags for a lot of us, I suspect. I grew up New England/Quaker frugal, so buying multiples of anything that's not a basic (socks, underwear) is a concept I've only encountered as an adult. I have three flannel shirts, and that feels extravagant. As a kid, I'd only have had one. But it's nice having different shapes, lengths, and colors. Same goes for shoes, but they're (usually) a larger chunk of the budget than tops. Also, shoes are, for many folks, much harder to fit than tops. I basically keep any shoe that fits comfortably and is aesthetically appealing to me, but my fit/comfort bar is extremely high. I think I have a dozen pairs of shoes all told, for a four season climate (not including my running shoes, which I don't wear casually since they already wear out too fast). I'd consider this a bare minimum from a fashion/style standpoint: two pairs per season to alternate between for everyday wear (extends longevity) plus one dressy pair per season for occasional wear. But, if you wear a lot of different pant lengths and styles, or if you participate in lots of events with a wide range of formality, etc, you automatically increase your shoe needs.
Janet -- so as not to totally derail, I really like those Freebies Sly's that Angie posted. They look like a great way to boost variety and have the potential to take both casual and dressier outfits in interesting directions. I have a personal stink eye for sporty sandals that aren't for sports, so can't comment on those.