Train to Gare L'Est
What train do I need to get to go to Gare L'Est from CDG? From there I hope to get a train to Croatia. Should I book my international train from the station or purchase it online beforehand?
Try finding a train ticket online before you go via this online European train ticket vendors.
To get from CDG Airport to Paris Gare de l'Est, take the RER B from CDG to Paris - Gare du Nord then you can either walk 5 minutes between stations or take Metro Line 5 direction Place d'Italie or Metro Line 4 direction Porte d'Orleans.
Best of luck,