To be honest dark circles can often be a hereditary/age thing unfortunately, & not much to do with sleep or dehydration,
Skindoctors Eyecircle would be a good one to try. It’s won many awards in the UK & I know a few people who have tried it & had good results. Also theres a Garnier Roll On Eye thingy that has caffeine & other energising things in it but tbh I found it worked great on my eye puffiness but not my circles. & I have said it many times, Dermalogica Total Eye Care is a fabulous eye cream as well but quite exxy, you should be able to get a sample though if you are interested.
Also a concealing product would be beneficial. you could choose something with a yellow tone but I would mainly recommend it being a liquid. The best concealer Ive used recently is Maxfactor Mastertouch. Also apply it where it is darkest, from the inner corner of your eye to about where your pupil finishes. This will help make an illusion that this darkness is nearly the same colour as the rest of your eye. If you apllied it the whole way the inner corner would still look darker in comparison (hopefully this makes sense). I also try to choose a concealer a teensy bit lighter than my skin tone to help with the illusion. With this particular product, because it goes on so well, you could apply it before or after your foundation or both if needed.
Hopefully this helps you out! Also with skincare be aware that it can take 3 months to get results you might notice. You’re best off taking a pic of before & then after once you’ve used the whole eye cream up, that will give you a good idea of what works for you.
🙂