Gorgeous dress!
Black and Navy is going to be big for autumn winter this year, it's usually a combination that's frowned upon however it's been seen everywhere at the moment.
If I were to wear that dress I'd wear it with a black blazer, it will smarten it up for the wedding and it'll be on trend,
As for shoes a navy or black platform would be nice, and you cant go wrong with a nice clutch bag, something glittery or studded in silver would be nice and silver would go well with your colouring and the dress (you could paint your nails silver too for a pretty effect).
Finally for accessories, something very demure like a silver chain or a watch is all you'd need.
In short, Id keep the over all look simple and pretty, black, silver & navy are gorgeous colour combos and you'll stand out but for the right reasons.

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