From Gare Saint-Charles in Marseille, you can take the train to Avignon. The regular trains (TER) takes about 1h20 minutes and costs € 19.40 per person (one way). It is best to get off at the station Avignon Centre which is located opposite the old city walls. A TGV train is much faster. You are in Avignon in only 40 minutes, but the TGV station is located a few kilometers outside the city. Better reserve your ticket in advance . It costs about € 29 per person (single journey). It's best to check the timetable before you leave.
TIP: If you take the TGV to Avignon you can use a shuttle bus from the TGV station to Avignon Poste, inside the city walls. A ticket costs € 3 per person and is valid for 24h. The shuttle buses run frequently.
How do I get to the train station from the cruise port in Marseille?
Gare Saint-Charles, the train station in Marseille, is located on Place de Marseillaises, outside the city center. The station is very large and busy. You will find both a metro, the regular trains, buses and the TGV station. The fastest way to go there is by taxi. The ride costs around € 30 per taxi (4 persons one way) and takes about 25 minutes.
There is a cheaper alternative using a bus-subway combination. For € 1.50 per person (one way) first take bus 35 to La Joliette (15 minutes). There you take the metro to Gare Saint-Charles (red line n°2 towards Sainte-Marguerite Dromel). The underground takes only 2 minutes and costs € 1,50 per person as well (one way).