I'm not really answering your questions but here's some random stuff:
Seles won the fifth tournament she ever played, beating Evert in the final. She then reached the semis of the French in her next tournament, only a year later she won the title.
Hingis and Venus were pretty much hyped from the moment they entered the tour, partly because the WTA had let them both slip through the AER net - Venus had an amazing junior record and Martina was a French open junior champion at age 12 I think.
Martina took a while before a stunning run in Hamburg before Conchita crushed her.
Venus showed her promise from pretty much her second match because she pushed ASV to three sets in the year that ASV had already won the US and French opens.
Mauresmo broke through in Berlin 1998 falling to Conchita in the final. She pushed world no.1 Martina Hingis to three sets at the US open before her famous grand slam final appearance in Oz the next year.
Aged 14, Capriati reached the final of her first tournament falling to Gabriela Sabatini
Lindsay I'm not too sure about - I don't remember well but she was certainly consistent and in the top ten within about a year and a half of her debut which was pretty rapid.