Most of the transfers to ski resorts operate to/ from Geneva Airport, rather than the train station (Cornavin), or at least they’re cheaper from the airport. So it’s worth checking with the transfer company, even though the airport is on the ‘wrong’ side of town. It’s connected to the intercity train network.

You can see times on www.bahn.com. A search for a random date suggests a few options, all via Milan. Some journeys involve a taxi, metro or 20 minute walk between two stations in Milan.

 If you’ll be using a railpass, you need to reserve the FR and EC trains in advance. If you’re paying cash, it’s definitely worth booking in advance, but how best to book depends slightly on which trains you’ll take.

You could also consider getting the train to Cluses. It’s an extra train, but a shorter transfer to Les Gets. You may even be able to get the bus from Cluses to Les Gets, and save the cost of a private transfer. I did that last year, although the timings only worked in one direction. (The bus timetables are generally designed to meet the TGV from Paris).

https://www.snowcarbon.co.uk/ski-resorts/les-gets/les-gets-transfer-guide

Thank you so very much for your detailed answer!! This is very helpful

No problem. 

Looking at the bus timetable, it departs from Cluses at 1815 Mon-Fri, 1840 Sat/Sun. So you’d be able to get that bus with an 0818 departure from Venice SL.