My absolute favorite place to find the cheapest materials for building fairy garden accessories is nature.
This past winter we made a patio set with our champagne bottle tops! (Yes, I did buy another bottle of champagne and drink it just to get one more top and the cork hahaha.)
Garage sales and thrift stores are a great place to find unique containers for fairy gardens. (I got the cute tea cup for my teacup garden at a thrift store!)
If you go to Dollar Tree in the spring, they often bring in cheap fairy garden accessories for less than 2 bucks each (if you don’t want to build your own).