Places between Marseille and Nice

Hello, first of all I wanted to let you all know that I have very little experience in traveling. I’m planning a 5 day trip to spend in total. I guess I could spend 2 days in Marseille and 3 days in Nice. But there seem to be a lot of places worth seeing between the two cities. So I was thinking of spending 1 day in each city and spending the rest of the trip in places between them. Can I get your opinions on this? And can I get some recommendations for specific places I should go?