I was given a ‘my breast friend’ pillow and it was fantastic. Firm, and clips around the back so the baby doesn’t slip down and you can use both hands and move around. They stop you stooping to feed too, so good for your back. I think they’re a bit pricey though.
I got the bestselling Amazon one (with stars on it). It's fantastic, kept its shape well and I still use it now, almost a year later. Also used it to help baby sit up when she was younger. Cost 12 quid I think.
After buying a few different pillows nothing was as good as a My Brest Friend pillow. As others have said above it was far superior and so so good for your back as it's quite firm and baby doesn't just sink into it.
I have a v shaped memory foam cushion from Argos, not a special breastfeeding one but works perfectly for me (fed DD1 to 23 months on it and now DD2 is feeding on it at 12 months. Think it was £25. I like the v bit to balance iPad on.