Back in the old days, cycletourists had this idea that they had to be entirely self-sufficient from the moment they rolled out of their start location ... that they had to bring everything with them. There are tales of people bringing large bags of rice and oats and things so that they never had to stop at a shop along the way.
These days, most of the places we tour have stores. You can buy stuff as you go.
I'll often start a tour bringing one wicking T-shirt ... and end up with about 5 of them by the end of the tour.
You can even start with one tent (or sleeping bag, or mattress or whatever), decide you don't like it for one reason or another, and buy another one halfway through the tour.
So yes, start light ... and if you find you are cold or uncomfortable or something ... buy stuff to solve the problem.