Ebay has really good quality wigs for affordable prices. They also sell wigs that you can use heat on, it's sometimes called Japanese Silk or KK Wire hair. They're almost just like human hair but alot cheaper.
I prefer the heat resistant wigs but after using them a lot they do tend to get tangled and matt more than human hair since they're synthetic. I think they sell products to help moisturize the KK Wire wigs but I haven't tried any - I manage the matting by brushing and straightening the wigs with a hair straightener before curling them again.
The reason why synthetic heat resistant wigs tend to matt or tangle is because they don't retain moisture, however they've created a new fiber called Protein hairs (it's not available in wigs yet, only in weft/hair extension forms). Protein hair is not human hair nor is it plastic. It's a man made fiber that's mimics keratin by using protein to mimic the structure of human hair. I've used Protein hair as hair extensions before and they retain moisture just like human hair, can be curled or straightened with heat which is great.