I played my first game since the Sighstone changes.
At about 6 minutes I had 800 gold. That's enough for a Sightstone.
Except I couldn't buy one. I was only half way to earning the Sightstone upgrade at that point (Frostfang). So I had to go back to lane with no vision besides my trinket.
Solution: Allow us to either BUY a sightstone*, or have the support items automatically upgrade once you hit the support quest.
You have both forced me into a build path, and at a time you deem appropriate. That's why I'm unhappy.
*If I'm doing well enough in lane to afford a Sighstone early, I should be able to buy one.