The stretch knit crepes normally used for dancewear have far less lycra in them, usually between 5%-7% whereas the 'lycra fabrics' are usually 20%. The description 'luxury' is often just used to distinguish one product from another. Chrisanne's Luxury crepe is 93% polyester 7% lycra while their Dance Crepe is 95% nylon 5% lycra and also called Luxury Dance Crepe at times.
The knit crepe is a lighter, finer textured fabric with more drape but less stretch overall. It's much better for skirts than lycra which gets heavy very quickly in any quantity. Both types may be nylon or polyester mixed with lycra but more often it's nylon for the lycra body/leotard fabrics.
Stretch mesh aka stretch net is a sheer fabric with some qualities of lycra and sheer wovens and almost as big a staple for dancewear makers as lycra itself. It's nearly always a nylon mix in my experience. Ideal for yokes above a sweetheart neck, very popular for sleeves and so useful to give discrete coverage by using mesh on a dress under body cutouts and plunge necklines (you see these on Strictly all the time). Like lycra it can have a raw cut on skirt hems (a big advantage over sheer wovens) and it has wonderful drape and movement for latin skirts from very full circle skirts to long elegant straight skirt with a split.
Rhinestones stick to mesh extremely well (not sure why but they do) and it's sometimes used underlined with lycra to give a stronger matt effect and a great base for embellishment.
Recently there have been some truly fabulous glitter and sequin fabrics appearing in DSI and Chrisanne Clover in particular, they made a huge impression on me on a recent visit to the Chrisanne Clover showroom where, unlike the DSI showroom, all their fabrics are on display. They have much more impact and power than the previous types I have seen over the years. They're expensive but if you usually use Swarovski or Preciosa rhinestones some of the cost may be offset by reducing those.
DSI and Chrisanne Clover are the big names in ballroom wear although funkifabrics is becoming increasingly popular for their huge ranges of prints and Crystal Parade has plenty of fabrics and trimmings as well as crystals. They all offer good quality fabrics as does Trim-It in Blackpool but at lower prices albeit without quite the huge number of colours and scale of fabrics - it's always a good place to start though with plenty of choice in general. All of these companies offer an excellent online service and although Trim-It doesn't have anything like the online information that some of the others provide.