There isn't any really any order to watch DC movies. But, the best order to watch them is in the order they came out.
If you haven't watched Batman series. Watch Batman begins (2005), Batman the dark knight (2008) and Batman the dark knight rises (2012). Btw, these movies doesn't comes under DCEU. But, it'll give an idea about Batman and his origin story. Movies are also good specially The dark knight (2008)
and then watch DCEU movies
1. Man of steel (2013)
2. Batman Vs Superman (2016)
You've already watched WW and Aquaman. So, the next movie is Justice league (2017).
DC movies are not as good as Marvel movies.