I think, "Andrey Ryblev" is his best film. It's one of the best films ever made. I recommend you to see "The Mirror" and "Nostalghia". They are masterpieces! "Ivan's childhood" is Tarkovsky fist film - one of the most interesting and imressive films about war. His last film "The Sacrifice" is the will of Tarkovsky. "Solaris" and "Stalker" are also very interesting. Unfortunately, Tarkovsky created only 7 feature films. They are all worth seeing! I think, best of all to see his films in the chronological order - you will see development of his "cinema language". Congratulations!
You will soon open new interesting imressive world in the cinema - world of Andrey Tarkovsky! 