Glow Maker, available on Maelove, $27.95
Maelove is a skincare company founded by a team of MIT grads (skincare obsessives, brain and cancer researchers, and chemical engineers) to make affordable, high-quality skincare accessible. The entire under-$30 line is surprisingly great, but this $28 vitamin c serum (which people have likened to the multi-award-winning $166 C E Ferulic Serum) is the real showstopper — and it keeps selling out. I personally use it, and it does a great job of reducing hyperpigmentation, hydrating, and adding a nice "glow" to the skin.
Shipping note: Maelove says you can expect orders in three-seven business days.