I can offer some advice, since I have a large collection. You have two options: Human or synthetic. Each have advantages and disadvantages.

Synthetic: Inexpensive for what you get. A 6 foot "Rapunzel" wig may be $50 or so. There are lots of vendors on eBay selling synthetic wigs. They tend to tangle easily, and the fibers will stretch and look ugly if you are not careful. They don't smell like hair, if that is important.

Human: Cost a fortune for a long hair wig. Raw hair prices have skyrocketed the past couple years. The eBay vendors I used have all closed, and what I see now isn't that impressive. Human hair wigs smell and feel like, well, human hair. If you are patient, a used wig may be a good option, but buyer beware. Read the listing carefully, and ask questions.

Hope this helps. Ask if you have more questions.