Hi and welcome to
MakeupTalk! I'm Maja from Slovenia.
Both dresses sound gorgeous from the descriptions. I would personally go with the purple one with gold sequins. It sounds more appropriate because of the darker colour and the gold sequins make it more formal and festive at the same time. I also like this one better, because the teal one has a shrug which IMHO doesn't look formal.
As for accesories I like your choice of a gold bag, but buy a small one, because you don't want to divert the attention from the dress. Shoes, well, you can go with gold or dark brown with purple undertones, but definitely not black or white.
Keep jewelry simple and gold or gold-like.
Now, for the hair, I'd keep it loose and simple, I think that would balance the colour of your dress and your accessories nicely.
HTH!