Dumb questions from first time traveller

[lynx]

Dear experts,

I am planning my first time trip to europe this coming june for around 2 months. I have kind of planned my trip and currently deciding whether to go to French Riveria (France). From Paris, I am wanting to travel to Lyon and then to Chamonix. From there I take the train across to Martigny (Switz) mainly for the views. I am thinking whether it would be worth me then going back to France and down to French Riveria and across to Italy OR stay in Switz and then travel to Italy.

Also, from reading the forums, users advice that you need to book hostels in advance. My question therefore would be how far in advance would you need to book ahead as June/July are the busiest periods?

Would appreciate it if you can help me answer these questions.

Many thanks