Ed's had costume changes several times throughout the manga. Sometimes he'll wear different clothes, like in the hospital or venturing out to Xerxes, but usually he only has one outfit. Mostly it's a combination of black pants, black undershirt, red coat, and some kind of black jacket/shirt.
First of all, his 12-year-old clothing:
His jacket has a rather noticeable large zipper. It has long sleeves. Also, his red coat has buttons that don't seem to serve a real purpose. He wears this costume when he first sets out to become a State Alchemist, and we can assume that whenever we see him wearing this it'll be during the early period of his quest.
His next costume is:
His jacket looks a bit like the old one except it doesn't have a zipper and it's sleeveless. His red coat still has it's buttons so possibly it's the older one. He's still wearing this when he's 15, so we can assume that when we see these clothes, it'll be during the middle-to-later period of the quest before the start of the manga. However, the jacket and coat get destroyed in Lior, so he has to get a new costume.
The ever-familiar clasp jacket. Also, his red coat has no buttons now, so maybe it's a new one in the same design? He wears this costume for much of the manga up until Volume 7, when yet again his jacket is destroyed in the fight with Greed. So he gets another one again!
So then we had:
The open front jacket. This jacket has a zipper and a place to buttom up the top, but we have never seen him actually close this jacket. It is forever open to the world. Sometimes he wears the red coat on top of it. He gets it near the end of Chapter 34, and he has it until AGAIN it is destroyed in his second fight with Scar. I think it's been established now that Ed has really bad luck with clothes!!!
So, temporarily, he throws it out for a plain black shirt:
He wears this less than two days before he also has to throw it out because it's drenched in blood and icky stuff (along with his longer-lived black pants). Poor black shirt. :(
Anyway, as of Chapter 56, Ed has started wearing very mature-looking clothes he got from the military (along with military-issued boxers). Will he keep this costume? Will he get a different one? WE HAVE YET TO FIND OUT!
And uh...getting back to the original topic, Where would the novels take place according to Edward's clothing?
Novel One apparently takes place during the middle-to-late period, when Ed is 15 years old. Observe the sleeveless jacket with no zipper:
Novel Two is hard to tell. Novel Three is also hard to tell. It seems Ed has his clasp-jacket on the cover of Three, but it's not very clear on Two. I don't know what the story is for Novel Three yet, but I'd find it incredibly difficult to imagine Novel Two taking place after Chapter 4 of the manga.
Novel Four apparently takes place during the early period. Behold the LARGE ZIPPER:
(EDIT: Kirsten says- "Novel four takes place when Ed is 13.")
And uh...I'm not getting into the other novels. I don't even know how many there are. >>; So The End.
EDIT 2: Also, Ed's gloves get destroyed more times than I'm going to bother counting. But Arakawa explained this in Hagaren DX- he keeps spare ones in his suitcase. :D