transportation in aix-en Provence

Hi guys, I am new in here~~~

I will spend 2 days in Province in June, to see lavender.

I have booked 2 nights hotel in manosque.

My plan is that spend 1 day in Marseille and 1 day in Valensole
on the third day , I will go to Paris from aix-en Provence.

I would like to ask the transportation problem.
What is the best way from Marseille to manosque and then go to valensole?

I found a bus route but it's a evening bus (manosque to valensole) and morning bus (valensole to manosque)

http://www.cg04.fr/routes-transports/transports/reseau-des-transports/index.html
Is there any better transportation?

Besides, I also found the car rental for just 25eur per day (pick up: Marseille, Return:Aix-en- Provence)

which one is the best?

Thank you all !