When I travel, I put my goggles in the supplied goggle pouch and put into my Helmet for safe keeping in my luggage or boot bag. I have a pair of Oakley Airbrakes with the quick change lenses and sometimes carry another lense with me. I just put it into a soft goggle pouch and stuff either into my pack or an inside jacket mesh pocket.
Your idea of carrying an extra lense is a good one but IMHO you will quickly tire with the hassle of changing a lense, especially on the hill. That is the reason I splurged for the Airbrakes. I can change a lense in less than 10 seconds, with gloves on! Other goggle makers are also introducing quick change lense goggles which is long overdue!
As this is your first pair of goggles, a little suggestion. Never and I do mean NEVER use a cafeteria napkin or bathroom paper towel or even a facial tissue to clean the lenses of your goggles! That would be like using sandpaper to clean them and will ruin the expensive coatings on your lenses, destroying them in seconds by putting tiny scratches all over the surface. Only use specific lense cleaning cloths that are usually a micro fiber. The soft pouch that comes with most goggles are usually designed to be able to be used as a cleaning cloth as well.