Recovering from a trip where one wet night made the whole setup feel inadequate

One night of sideways rain exposed every weak point in our setup. The tent stayed standing, but our bags were damp, the cooking area disappeared and wet layers ended up mixed with dry clothes. We packed up miserable the next morning. I'm not ready to buy a whole new camping kit. If you were rebuilding your wet-weather routine after a trip like that, what would you change first: campsite selection, shelter layout, packing, or clothing?