I've come to sing the praises of Vitamin C sheet masks
In an old thread, someone suggested taking sheet masks on business travel after I asked how to look somewhat presentable and I got a vitamin C mask on a whim. Was blown away by the result and now got some more. Definitely not a one-off result, my skin looks about ten times better today than it did yesterday evening, much more even skin tone and generally glowing and hydrated. It was a cheap own brand mask from the dm drugstore chain, one sachet is 95 cents and they are very wet and there's still serum left in the packet that I'll use tonight.
I don't use a vitamin c serum, maybe the effects are similar, but I'll definitely keep them on hand from now on. If I need to go anywhere and want to look nice, I'll just throw one on.