我的最喜欢的衣服。

It is almost flawless! I am just trying to write in a more natural way. 

我在工作必须穿着一件西服。我工作的时候必须穿西装/我在工作时必须穿西装。 穿着一件西服 is a bit wordy;在工作 is incomplete, you need to add 时 at the end, unless you are saying "I am at work" 我在工作.

我周末喜欢穿一件毛衣。It is correct, but 我周末喜欢穿毛衣/在周末我喜欢穿毛衣 is less wordy, unless you want to emphasize 一件. Jumper is actually 针织衫, a type of 毛衣 I think.

我的最喜欢毛衣叫Aran。我最喜欢的毛衣叫Aran毛衣（阿兰毛衣 in Mandarin）Pay attention to where you need to put 的. There shouldn't be too many 的 in one phrase, ususally it is put in front of the object you want to describe. So I won't write 我的最喜欢毛衣，but 我最喜欢的毛衣.

Aran毛衣是一件传统的爱尔兰的毛衣。Aran毛衣是一件传统的爱尔兰毛衣.

从来自Aran岛 , 很小岛， 在爱尔兰西边。它来自Aran岛，很小的岛屿，在爱尔兰西边/在爱尔兰西边的小岛（Also, here I put 的 in front of 小岛, the final object I want to describe）

爱尔兰人平时穿白色Aran毛衣。爱尔兰人平时穿白色的Aran毛衣

但是我的脸很白， 所以我喜欢蓝色或者黑色的毛衣。Nice.

很多商店在爱尔兰卖Aran的毛衣。Nice, but you don't need 的 after "Aran" here.

但是我妈妈做我的毛衣。I prefer 织我的毛衣, 做毛衣 just sounds a little strange to me.

爱尔兰的老人喜欢编结毛衣。 喜欢编织/喜欢织毛衣
My favourite clothes.
In work I have to wear a suit. At weekends I like to wear jumpers. My favourite type of sweater is a called an Aran sweater. Aran sweaters are a traditional type of Irish sweater. They come from Aran Islands, small islands on the west of Ireland. In Ireland people usually wear white Aran sweaters. But my face is very white so I like to wear blue or black sweaters. In Ireland lots of shops sell Aran sweaters. But my mother makes my sweaters. I Ireland elderly people like to knit.


Still trying...

Congratulations! Really almost flawless! Just pay attention to the place of 的, and some of the word orders.

                       我的最喜欢的衣服

我在工作时必须穿着一件西服。我周末喜欢穿一件毛衣。我的最喜欢毛衣叫Aran。Aran毛衣是一件传统的爱尔兰的毛衣。它产自Aran岛 , 很小的岛， 在爱尔兰西边。爱尔兰人平时穿白色Aran毛衣。因为我的脸很白， 所以我喜欢蓝色或者黑色的毛衣。很多商店在爱尔兰卖Aran的毛衣。但是我的毛衣是我妈妈给我做的。爱尔兰的老人喜欢编织毛衣。
My favourite clothes.
In work I have to wear a suit. At weekends I like to wear jumpers. My favourite type of sweater is a called an Aran sweater. Aran sweaters are a traditional type of Irish sweater. They come from Aran Islands, small islands on the west of Ireland. In Ireland people usually wear white Aran sweaters. But my face is very white so I like to wear blue or black sweaters. In Ireland lots of shops sell Aran sweaters. But my mother makes my sweaters. I Ireland elderly people like to knit.


Still trying...

I am sorry about correct  in your orgin article,please forgive me.

我的最喜欢的衣服。

我的工作要求必须穿西服（西装）。我周末喜欢穿毛衣。我最喜欢毛衣叫Aran。Aran是一件传统的爱尔兰毛衣。他来自Aran岛 , 一个很小的岛， 在爱尔兰西边。爱尔兰人平时穿白色Aran毛衣。但是我的脸很白， 所以我喜欢蓝色或者黑色的毛衣。在爱尔兰很多商店卖Aran的毛衣。但是我妈妈给我做毛衣。爱尔兰的老人喜欢织毛衣。
My favourite clothes.
In work I have to wear a suit. At weekends I like to wear jumpers. My favourite type of sweater is a called an Aran sweater. Aran sweaters are a traditional type of Irish sweater. They come from Aran Islands, small islands on the west of Ireland. In Ireland people usually wear white Aran sweaters. But my face is very white so I like to wear blue or black sweaters. In Ireland lots of shops sell Aran sweaters. But my mother makes my sweaters. I Ireland elderly people like to knit.


Still trying...

我的最喜欢的衣服。

我在工作时必须穿着一件西服。我周末喜欢穿一件毛衣。我最喜欢的毛衣叫Aran。Aran毛衣是一件传统的爱尔兰毛衣。来自Aran岛 , 是个很小的岛， 在爱尔兰西边。爱尔兰人平时穿白色Aran毛衣。但是我的脸很白， 所以我喜欢蓝色或者黑色的。很多商店在爱尔兰卖Aran的毛衣。但是我的毛衣是我妈妈做的。爱尔兰的老人喜欢编结毛衣。
My favourite clothes.
In work I have to wear a suit. At weekends I like to wear jumpers. My favourite type of sweater is a called an Aran sweater. Aran sweaters are a traditional type of Irish sweater. They come from Aran Islands, small islands on the west of Ireland. In Ireland people usually wear white Aran sweaters. But my face is very white so I like to wear blue or black sweaters. In Ireland lots of shops sell Aran sweaters. But my mother makes my sweaters. I Ireland elderly people like to knit.


Still trying...

我最喜欢的毛衣

工作的时候我不得不(have to)穿西装，但周末的时候我却喜欢穿毛衣。我最喜欢的毛衣款式(type)是Aran。Aran是爱尔兰毛衣的传统款式。他来自爱尔兰西部Aran小岛上。爱尔兰人喜欢穿白色Aran毛衣。但是蓝色或者黑色的毛衣更适合我白色的皮肤。在爱尔兰可以在很多商店买到Aran毛衣。但是我穿我妈妈给我织的毛衣。爱尔兰的老人喜欢自己织毛衣。