One of my most recent disappointments is that Collection filter finish dupe. It made my makeup sit badly and am fairly sure it also broke me out. I can't imagine just using it by itself, as someone who isn't blessed with naturally clear and smooth skin, it wouldn't do a lot other than add a bit of a sheen.
I wouldn't repurchase it but I will say that I do like it as a subtle highlighter on top of makeup, so will use it up in that way.
My most useful recent buy is probably the Simple Water Boost Hydrating Booster - I add it to foundation to sheer it down and add hydration (without any greasy feeling) and it's brilliant and makes everything so blendable. Also works very nicely as a cheap hydrating serum in general.
Also really like the new NYX Fat Oil lip oils - cheap and just really easy and subtle.