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Hello, I'm fairly newish to patterns & would very much like to make Pattern #83850 as a gift. How much thread do I need? And do I fold the strings in half and loop or do 16 separate threads? It's for a man's wrist. Also, how do I repeat the pattern when it ends in a different order than it starts? Any help would be greatly appreciated! :)

Hello, welcome to this site.
Since it is a odd number of strings from each colour and you are new, I won't make a loop. You can just fix your strings and start knotting or you can make a shaped start like this https://www.friendship-bracelets.net/tutorial.php?id=5250 even without a loop, just braid your ends. When a pattern repeats in a different order than it starts you just start knotting from the beginning and ignore the colours, but your pattern does repeat with the right order.

I hope it helps you and happy knotting.

Thank you Stefanie! This site is amazing. How long should each strand be? I'm clueless when it comes to length :/

You could also use the "Safety Pin Start" from the tutorial (( How to... )) Safety Pin - Easy way to start bracelets.
Because you are making a 1-2-1-2 style normal bracelet, tie your lark's head knots with both a white and black string side by side in each knot. this will result in your first row staring with
W-B-B-W W-B-B-W W-B-B-W W-B-B-W
Then use full forward or backward knots in this first row so that the string colors are lined up correctly (like the pattern) for the next row. (w-b-w-b w-b-w-b w-b-w-b w-b-w-b)
Also note that the rightmost string color will be black instead of white, but this string should be completely hidden because all of the knots will be tied using the white string.