It will really take a lot of time to see results for any of those products but Dan's AHA+ is nice for dark marks over time. Though you have to use very sparingly.

I use honey and lemon masks every other night for about 45 minutes and it does wonders! I don't really measure out how much of either but I would say about 1 part lemon juice to about 3 parts honey. It's super cheap, effective, and leaves your skin healthy and glowing. It heals up active pimples at the same time as it lightens dark spots.

Let me know what you try and how it works for you. I hope I was of some help!