Depends what you want it for. For a "ta-da" noticeable difference you need one with active ingredients
Most Vit C ones work, and almost instantaneously. The vit C content needs to be high, and it's very volatile so tends to be a keep- in the fridge and with an expiry date.
I love love love the Vichy vit C (has massive stupidly long name) It transformed my skin almost overnight. Gives that glow. Heard good things about Garden of Wisdom vit C with ferrulic acid (makes it work better) too. The Ordinary vit C is the foulest product ever made and resurfaces your skin by having its top 10 layers scratched over with a sand in cream texture.
If you want moisture and plumping, you want a hyaluronic. Any will do, just make sure you add it to damp skin as it works by molecule binding or something technically sounding. I've tried numerous ones, I like Vichy 89 and Nip &Fab Dragons Blood best. Again, problem with HA serums is they are a bit slimy. They do plump though if used correctly
If you want wrinkle reducing you're going to have to go with retinol, and few creams/serums on the shelf market are going to have a high enough concentration to do anything.
For a general all round serum, the Boots Protect &Perfect and its spin offs take some beating. They are silicone heavy, so lots of smoothing and plumping. No actives as far as I know, but very good IMO. I tried the Boots labs one over the summer and that was very good
I've tried cosmetic counter ones, Chanel, Clarins , EL night repair but never found one that I'd repurchase.