I completely agree with Vulcon that Ryze is a good beginner pick being ranged so gives your a little bit of distance between the opponent champion but that Pro is sometimes what can be it's downfall. It is a magic-type of ranged attack so you have to be very smart with your Item picks to make sure you are building AP and also his Maximum Mana is what stat is used to figure out the bonus's for almost, if not all, of Ryze's Abilities.
The other Con that I saw when I was using Ryze as a beginner, thus making more mistakes, with him being a Range, Magic AP based character he is extremely squishy in the beginning and the greediness that sets in to add to your mana pool is sometimes your downfall for this character early on.
But this is just my level 11 newb two cents so take it with a grain of salt...or sliver of mana.
TL;DR--> Ryze ultimately is a good pick early game due to being Ranged and easy to use...He is also very squishy until your certain build is completed