Here I will list online shops you can use for cosplay! I tested all those shops.
Sewing patterns
Butterick Mc Calls VogueA complete collection of sewing pattern which can use even by sewing beginners! There is a collection for ultra easy level, up to complex projects. I tested both simple (fast and easy colection), normal and average level: all instructions are clear and illustrated. Great detail: all sewing patterns instructions are in French and English, and some have Spanish version too!
Update: they created a whole new
cosplay sewing patterns shop!
Good: the diversity of sewing patterns, several linguage version, the different levels available. Detail: register to their newsletter to know their regular promotions operations!
Bad: maybe not the best if you are looking for Historical accuracy.
There is also
Simplicity sewing patterns: I have never tried them but they have lots of costume sewing patterns.
They can also be bought
hereIt has an amazing
Zelda cosplay sewing pattern!
Wigs
CosplaydnaHigh quality wigs for cheap! Mostly unstyled wigs made of kanekalon or high temperature resistant wigs.
Colors are varied but
their wigs fits big heads. plus: free shipping, resin skin top which makes hair parting possible, Tangle and Frizzle Free, High Fiber Count
Cosplaywigcosplay wig: styled wigs, good quality
Be careful of the wig size and shipping time which can be awfully long!
Update: I don't know if this shop is as active as before: nowadays it seems to be totally empty.

Wig fashion can be also found
on ebay or
hereGood: great choice of base wigs. I love their quality and their cheap prices!
Wigs fit even large heads wig feverGood: cheap but quality wigs!
Notice: I think it's the same seller as wigfashion, sometimes the prices vary.
Ayanamisatorou wigs are often recommanded but I have never tried them.
Arda is a USA based shop:
Good: they have ultra good quality wigs. They fit well big heads too.
Careful: they are a bit expensive.
Epic cosplay wig is also based in the USA. I head good comments about their wigs!
The five wits: accurate wigs but some are a bit expensive.
Fabrics shops
I live in France and I never used any usa fabric shops. Here are the shops I use:
Tissus PriceA french shop: serious, reliable, quick shipping, fabric is great and not expensive. My favorite fabric shop!
Good: price, quality, variety of colors and type of fabrics, ultra serious seller.
My fabricsShips to: Germany France, United Kingdom Austria, Belgium, Denmark, Luxembourg, Netherlands Italy, Monaco Sweden Norway Andorra, Czech Republic, Finland, Greece, Hungary, Ireland, Liechtenstein, Poland, Portugal, Slovakia, Spain, Switzerland Estonia, Latvia, Lithuania, Slovenia Bulgaria, Croatia, Iceland, Turkey Canada, United States of America
Goods: the variety of fabric, the diversity of colors.
Bad: long time to receive/ship the packages.
A new
lace applique shop I discovered on aliexpress! It has hundreds of lace, applique, easy to use for cosplays such as Trinity Blood. Prices are very cheap!