Which should be my first heels ??

I've been going back and forward for weeks, which one should I go with.

The first options are slingback 7cm mules heels OR

The gray block heels are 9cm.. yes I know.. hear me out it's charles&keith and it's used, for less than 10$ which I think is such a steal.

But I'm worried I won't be able to use it.. but I do noticed my foot doesn't hurt it when I wear 3cm wedges rather than a flat sandal/shoes.

I'll only wear the heels going to the airport and malls, or church, that's it.

around 1-4k steps chill walking with lots of rest.

I asked my mom for some feedbacks and she doesn't like heels so she hates all my choices, but I'm obsessed with heels since I was a kid and wanted one for so long.

Which one do you suggest me getting first? the 9cm 10$ C&K? or get a new pair of shorter heels that's a slingback?