however in terms of "Patterns" I will tell you Tidus was the very first cosplay I ever made from scratch 2 and a half years agao and what I did at least for the shorts was I went out to goodwill and found shorts that fit well and had large pant sleeves( don't worry about color, texture, or design at this point). then I hemmed them to the length I wanted and cut them apart at the seems for a pattern. then I traced them onto a nice black material and remade the shorts.
also for the vest, it's actually a really easy pattern to make simply because Tidus's vest doesn't naturally fit well in game and is held up by the belt. just make a rectangle that has the length of the your waist measurement. the back part is also lower then the front and is attached by a zipper. I'll leave it to you to figure out the rest of the pattern on your own because it's a simple design, just a pain to explain >>
finally on the shirt, personally I just edited a white sweat jacket i found a goodwill (though nowadays I'd probably just make a pattern from it.) the front part of the shirt cuts off just below the nipple and (IMPORTANT) is higher in the back. I say this only because I personally screwed this up andonly recently fixed it. when shortening the jacket, it'll naturally fall lower in the back, but this will not only hide most of your skin, but also will pinch the shirt in a weird way. I also sewed each pin stiripe on individually, but you can propbably just sewn on one yellow piece and make sew lines to imitate it. Also, tchnically the shirt has 2 sleeves, but the sleeve will bunch up in the armor so personally I cut it off.
anywoh if you have any specific questions don't be afraid to ask. I like to help out.... just once again I have no intention of making a personal tutorial or doing research for others. It's just kinda a pain and ultimately everyone works so differently that if you tried to follow how I did it exactly, you'd probably do a much worse job then if you followed your own instincts. trst me, some of the worst mistakes I've made have been the result Of trying to follow someone else's work too precisely.