Amelia Earhart wanted to teach all women and girls that they could be just as good, and better in the activities that men did. She was an active feminist, strongly believing in women's rights.
When Earhart got married to George Putnam, she referred to their relationship as a "partnership with dual control." On their wedding day, she hand delivered a letter to him that said "I want you to understand I shall not hold you to any medieval code of faithfulness to me nor shall I consider myself bound to you similarly."
"Flying might not be all plain sailing, but the fun of it is worth the price."
I think that Earhart means that not everything in life is easy, but completing what you want to gives you the satisfaction
"Never do things others can do and will do, if there are things others cannot do or will not do."
I think she means that you should be original and take risks to do things that other people can't do.
"The most effective way to do it is to do it"
I think she means if you need to get something done, get right to it, that's the easiest way.