Venus? A floating colony in Venus's atmosphere is the very definition of "fail deadly". Anything goes wrong you are dead, whether dead quickly or dead slowly. Plus, given the conditions on Venus, if there ever was an ecology, it has long been reduced to ash. It is also not likely we could terraform Venus (reduce the atmosphere and spin it up) given the resources of the entire solar system to do so.
If I were planning humanity's journey to the stars, I'd go with the moon first, followed by Ceres. Resource rich, low gravity, and far enough out of the Earth's (in the moon's case) and the Sun's (in Ceres' case) gravity well to make exploring other places much easier.