If you are planning to visit the magnificent Château de Versailles during your stay in Paris I would truly recommend you to do it during its most exciting state, that is to say when the fountains are sprouting water and Baroque music is played in the background. This happens only during the weekends if you do your visit between April 2nd and October 29th but also Tuesdays during a certain period and some additional bank holidays (2019, for exact dates make sure to visit the website prior to your visit). These days your visit will be even more spectacular as you will be able to enjoy the Musical Fountains show in the gardens of Château de Versailles. During the Musical Fountains show a selection of the fountains will come alive sprouting water to baroque music letting you travel back in time.
During the weekends the lines can be long so I would advise buying your ticket online, 9,50€ (which is also the cheaper alternative than buying at the ticket office, 10,50€). The gardens open at 09h00 and I usually go there at that time in order to enjoy the gardens before the crowds are entering after their visit to the castle.
Before your visit, make sure to download the map over the garden which also includes the location of the different fountains and what time they will be sprouting water. This will make your visit easier and you will effortless be able to prepare your itinerary and make sure not to miss any fountain.