Alright tagnut,
Good luck with building your basha, like a few guys have said, do a search and you will find several variations on setting up a basha, height will depend on whether you are in a hammock or on the ground. Style is what you prefer or part determined by the weather.
For the lines, I use good ol' genuine para-cord. I have 4 lengths of around 13ft, and 1 of just over 20ft. Up to now in the 6 years, I've been bashrin up I've managed with these lengths with nil probs.
Trial and error, you'll find the best ones for you.
Enjoy