Summer social gathering-what to wear?

It’ll be early summer in the evening. I’m attending an Asperger’s social event with my bestie, in an attempt to make new friends with other people with Asperger’s. It’s an end of year dinner party. What should I wear? My cleavage showing black tulle dress, cleavage showing blue tulle dress, or more conservative, but still very nice, blue short sleeved tiered dress?

Summer social gathering-what to wear?
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