The itinerary lasts 8hrs 50min, and has 3 steps, and it will cost 73 euros minimum.

Clermont-Ferrand - Lyon
The step from Clermont-Ferrand to Lyon lasts 2hrs 20min. You'll travel in a regional train.
You can find tickets from 42 euros if you book 2 months in advance.

Lyon - Nice
The step from Lyon to Nice lasts 4hrs 30min. You'll travel in a TGV Inoui operated by SNCF Voyageurs.
On board, you'll have access to: Wi-Fi, Drinks and snacks, Bike.
You can find tickets from 30 euros if you book 2 months in advance.

Nice - Auron
The step from Nice to Auron lasts 2hrs 00min. You'll travel in a day bus.
You can find tickets from 1.5 euros.