I confess, I have been going wild in Charity shops recently - and entirely on treats for myself.
I bought a vintage 1960s/70s/ Jaeger summer dress in linen, fully lined and as good as new. It fits, it still looks very stylish (according to DD and DDiL, DDil might be inclined to be kind, but DD is generally brutally honest). It cost £40.
I then spent most of the Autumn looking for a new winter coat, I could find nothing I liked, when I walked into a local Charity shop. Hanging up was a similar-aged fake fur winter coat, three quarter length, little worn, in perfect condtion and weighing a ton. It fitted and was mine for £15. It is so warm and I have been so glad of it this last week!
However this thread is about the £5 challenge. I did also buy two skirts; a practically new M&S one and one from the USA, both came in well under £5.