Hi - I’m in the UK and I usually buy my wadding or batting from EBay.
When I first started quilting I used polyester wadding sold by the weight and metre. I went for a 2oz weight and bought a couple of metres. It was cheaper than named brands and as I was just started out I didn’t want to spend a lot on something I might not be able to do. I’ve also tried the 4oz weight but find the increased thickness difficult to work with.
When I got more confident I made a play mat for my grandson - and bought a named brand - Hobbs Poly-Down premium polyester. It was more expensive but much nicer than the cheapest wadding. I have also bought from a local quilting shop. They tend to be expensive but you get to see what you are buying and you can get good advice from the staff.