I'd start from volume 1 because there is a lot of things that were left out, added in, and changed in the anime. Including: Character development, relationship development, story development, characters personalities, and who characters really were. The anime only covers up to volume 6, but has the addition of Hiro's story and the Yuki fan club president's story from volume 7 and Ritsu's story from volume 8. So when tu read those chapters tu will get a different feeling from them then tu did in the anime. Same thing applies to the episode where Tohru and Yuki visit Ayame's shop, that happened in volume 6 but it took place after Kyo's segundo form was revealed, and Yuki was trying to get away from Kyo, which is why he visited Ayame's shop. Besides all of the above, the reason I say to start with volume 1 chapter 1 is because there are things that are VERY important to the series that are in the first 6 volumes of the manga that are completely left out o changed in the anime. Like: the first half of the valentines día episode (episode 11 for anime, chapter 15 for manga), the part where Kagura's trying to get Kyo to eat her chocolate in the anime does not happen in the manga, instead Kagura is trying to get Kyo to go out on a fecha with her the siguiente day. The segundo half of chapter 15 (which has a lot a character development for Kyo and relationship development for Kyo and Tohru) is completely left out of the anime and instead the anime jumps right into chapter 17 (Momiji comes over and tells the foolish traveler story), completely skipping chapter 16 where we learn a lot más about Shigure.
There is a lot más that was left out, added in, and changed in the anime (including things in the first volume) so I beg of tu start with volume 1 chapter 1, it will make the series SO much better. Also, there is a group of voice actors (mainly fans of the series and are not professional, but still really good) that are making a radio drama version of the series that is actually going to stick to the manga. Currently they are up to chapter 24 and are hoping to do the whole series if it's popular enough. So I'll leave a link to their web site. But yeah, start with volume 1 chapter 1 and if tu want to tu can check them out.
Their web site:
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