I was searching and I found this thread. I know its a little late of about almost 2 months but the I'm posting the following as a semi more complete list than what is posted above.
Monster Kills and Minions:
Silver and gold data is from the quote above and platinum data is from what I notice on profiles in the game by cross referancing the people on my friend's list.
To answer the above poster's question, the ratio is as follows:
Looking at the above table and my personal stats, unless you constantly play support you should have no problem hitting the targets around the same time. Wins and take downs go hand in hand. Take downs include kills, assists and towers destroyed so you should easily have a 10 to 1 ratio by the time you approach platinum status unless you are mainly support.
I suggest all new players try all different forms of characters, especially since they are rotated approximately once a week. Having one favorite is nice but if he's chosen to be removed from your match or he's nerfed, you'll be upset you didn't diversify your options.