I usually use straight mono tied with a nail knot to the flyline then use a surgeon's loop knot to work off of. Depending on where I am fishing from I will 25lb tapered to 15lb leader for back bay/surf. I will go straigtht to all 25lb if the surf is big and fishing low tide off of jetties. Most lengths vary from 5-6ft total. When using big flys you can shorten your leader lengths. Always carry spare leaders. You will have to play around with what lengths suit why you are throwing. Good luck.
Dave is right. You can if you want. When I first started I did and then started using straight mono and have never gone back. I just use lighter weight line when using real small flies for smaller fish. Keep it simple and have fun. I put a small clip on the end of my line for ease of changing flies, but don't tell anyone.