It's obvious that if you start with smaller age you'll get more APs and pints on STR, INT and things like when you lvl up~
while little kids are also more difficult to play cuz they have a fraction of starting status than those olders.
So it's really your choice.
Well, tips : good years to choose: 10 (if you can handle it), 14 (a good one for beginning gamers), 18 ( if you really not familiar with games)
^^Enjoy