Well, I've been into this stuff for a very long time and I can give you some valuable advice, for sure.
"I have no idea how to coordinate clothing"
...This is not a strictly transgender problem. Every girl/woman goes through learning this stuff (many never do). If you can access this website you have a world of fashion information at your fingertips. Google "fashion blog". Bookmark them and spend a few minutes a week reading what people are wearing. As unimaginative as it sounds, nobody every went wrong by emulating a celebrity's look-- and with very little effort you can do it for little money if you forget about designer labels.
"...or what to wear to look more feminine"
The best thing would be to bring some friends into the project. There's nothing better than an outside opinion. It's very hard to do these things alone. Take selfies of yourself full length and compare the images to those of women you admire, considering what improvements need to be made.
"...social anxiety"
This is something that will cripple your entire life, not just the TG stuff. As soon as possible start seeing a good therapist about this. This is something else everyone must deal with to some extent and is entirely fixable.
"I have measured myself for my sizes but I really do get confused when looking up clothes online since there are so many different ways to give a size."
Again, welcome to the club. There are no firm standards for sizes in womens clothing (most men's either, really). Sizes can even vary within a brand. If you must buy online, I suggest buying from one of the reputable dealers that offer free returns. I surveyed this recently and these online clothe dealers are all meet those specs: Asos, Macy's, Zappos, Gap, Old Navy, Banana Republic. I buy from Macy's online all the time and they have a lot of good specials.
Here's something anybody who wears clothes should do: find a tailer to do alterations. It's not as expensive as you might think and there's nothing like getting clothes custom fitted.
"I am fairly tall and thin"
You're an inch shorter than my favorite current fashion model, Karlie Kloss. Karlie was awkward and pestered in high school because of her height and now she's adored by millions. Do a Google image search of Karlie Kloss + "fashion". You could probably wear any look she can.