I generally wear four.
On my left ring finger, I wear my engagement ring (a sapphire set with diamonds). It was a "one of a kind", and we had a wedding band made to fit with it, which is gold and diamonds. Then on our first anniversary, DH gave me a diamond anniversary band, and I wear that as well. In the summer when it's really hot I often just wear the anniversary band, as the three rings can get uncomfortable when my hands swell from the heat.
On my right ring finger, I wear either a diamond solitaire DH gave me a few years back, or a beautiful amethyst in a unique setting that I bought for myself years ago, or a blue topaz that I've had for years.
I generally don't wear rings on any other fingers. My fingers are very long, so have I have no problems with larger rings/settings overpowering them.
Anne