what is the best putfit for civil wedding?

You mean outfit? well it depends, if you are a guy, then use casual or formal attire, as long as you are comfortable. A white long sleeve with black coat as outer outfit, paired with black slacks and shoes is perfect. For a lady, I dont know because I am not a lady, but It feels good looking at a woman with a single colorful dress. Congratulations in advance. Go yeah and multiply.