"Ranking" as you mention it, is purely about points. The more quotes you solve, the more points you get, and the higher your rank.
If you no longer care about your percentage solved, set yourself a maximum time you'll spend on a quote. Maybe it's 2 minutes, maybe 5. That's the best way to get the highest number of points per play time.
Hope this is the advice you want.
Slotted spoons don't hold much soup. - Stephen Sondheim