The single most useful thing to know before buying heels is that the height matters far less than where the heel sits under your foot. A heel set slightly forward, under the ball rather than the back, will carry you across a car park without the ankle wobble that ruins an otherwise lovely shoe. Check that before you check the inches.
Heels earn their keep in the gaps between seasons more than in high summer or deep winter. Spring and early autumn are their best months, dry pavements, an evening that's cool enough for tights but warm enough that you're not bundled up to your chin, a wedding or a work do where you want your legs to look like you made an effort without freezing on the walk there. Summer weddings on grass are where most heels come unstuck, literally, so a thinner strappy heel is a gamble on anything but a hard floor, while a block or kitten heel will sink far less dramatically if the venue turns out to have a lawn. Winter is where I'd reach for something sturdier still, a block shape with a bit of grip, because black ice and a stiletto tip have never once got on.
The styling question people get wrong is thinking heels only go with dressed up outfits. The ones that actually get worn are the ones that go with what's already hanging up, so a plain block or kitten heel in a neutral colour will sit under straight trousers for the office, under a midi skirt for dinner, and under jeans on a night where you want height without the faff of balancing on four inches of nothing. A strappy heel wants a bit more drama around it, a slip dress, bare ankles, something that justifies the extra attention the shoe is asking for. Brown reads a little softer with denim and knits, black does everything else, and white, if you're brave enough, wants a summer outfit confident enough to carry it.
If you own none of this and want one pair that does the most, start with a black block heel at a height you can walk a full evening in without changing your gait by the second hour. It will survive wet pavements, cobbles, a long dinner, and most dress codes without you having to think about it twice, which is more than I can say for the strappy pair I bought for a wedding and wore for exactly forty minutes before switching to flats under the table.
This suits anyone who wants height on their terms rather than the shoe's, which, if I'm honest, is most of us.