What do you crochet with?
I mostly use tuff-cord because it is more durable to wear and tear than silk. Neckstrings are not delicate, and the only time I have ever had one break is when one of the tips got stuck in something--like bending over a wrought iron table or something.  I often crochet chain with thread which  increases the strength even more and is great for heavier or more rough cut, heavy stones. 
What is Gold Fill & Gold Vermeil versus Gold Plate?
Gold Fill and vermeil are wonderful  affordable alternatives to 14k gold which is why i use them. Gold-filled jewelry has 100x more gold alloy than gold plated and because that layer is so much thicker, it means gold-filled jewelry lasts longer and stands up to wear and tear better than gold plated. 
Instead of being dipped in gold, Gold Filled jewelry undergoes a mechanical bonding process that melts a thicker layer of gold onto the base metal. By law, gold filled jewelry must contain 5% gold by weight to be categorized as such. Gold Plate has less than 1% gold content and may have initial luster but fades and is easily rubbed off. 
Gold Vermeil is a common type of gold plating, which uses sterling silver as the base metal. Vermeil is more hypoallergenic and has a thicker layer of gold than normal gold plating, which is why you'll see it in stores selling fine jewelry. 
Neckstrings Jewelry works with gold fill and gold vermeil 
Most fashion jewelry is gold-plated, making the cost lower.