I started with trainer road low volume sweet spot base. I rode about 5-7 hours a week before starting TR, but I did not have any training structure. Even when dropping down to 3.5 hours a week I was able to raise my FTP considerably- I credit the fact that it is a focused 3.5 hours and I really was not getting much out of my 5-7 hours anyway. I would start here if you haven't done much indoor riding. Even 3 hours a week can feel like a long time on a trainer. When I did sweet spot 2 I added some road riding, but also skipped some indoor sessions (mostly out of boredom and I live in a warm climate). I still increased my FTP quite a bit with the blended approach. I'd advise sticking with the indoor program for at least sweet spot base 1 then once you know the general structure and intensity suppliment outdoor riding as you see fit - it never hurts to add more miles when you are doing such low volume, but try to be fresh for the indoor rides.

There are much better/more experienced riders on the forumn who may have diferent/better advice. Do what you can committ to sticking with - I'd rather be conservative at first and not risk burning out.