I bit, too.
After googling what the heck this all was, I ordered an inexpensive serum (that had a ton of good reviews) and the same 0.25 roller. I started using the serum, about a week before the roller arrived, and saw improvement in the overall look of my skin. I've used the roller 4 times, so we'll see at the end of May! I'm already looking at getting the 0.5. I'm afraid that I'll chicken out of increasing the length, for the collagen production boost. Too stab-y!
I'm terrible at keeping up with routines, so the inexpensive products won't make me feel guilty if I slack off on it.