I have been in your same situation, and my piano teacher started me out with the Etude Op. 10 No. 3. It's not too difficult, and it's a VERY important cornerstone, teaching phrasing and melodic line. That's something you'll need for almost every Chopin piece. For finger dexterity I recommend the No. 5 Etude from the same opus, and that one is a fun one!