The argan oil is a must. I actually don't use it topically -- I mix it with my leave-in conditioner. The Ordinary's marula oil is fantastic. Marula oil is a very simple and easily sourced oil, and it should never cost $72. Their rosehip oil is good and the price is fantastic, but it's not my favorite (RIP to Sunday Riley's Flora). NIOD has some excellent products on a smaller scale and at a higher price point, but those are definitely still a good value. I recommend CAIS.I use The Ordinary argan oil (I think they had a marula oil before too? I swear I bought a bottle from Sephora a while back). For eye serums, I really like NIOD's fractionated eye contour serum.
I love Timeless Vitamin C serum but I highly recommend buying it directly from the Timeless web site. It arrives extremely fresh and lasts for months in the refrigerator. I also love their Matrixyl Synthe'6 and Coenzyme Q10 serums. If you sign up for their emails, a few times a year they will have sales where they offer special deals on serums.Vit C actually should smell disgusting, but I don't blame anyone for finding it prohibitive. For vitamin C products, I've used DE (several repurchases) Paula's Choice, Skinceuticals (outrageously overpriced), Cosrx (highly recommended), and Timeless (Amazon purchase, risky). I also keep my vitamin C products in the refrigerator to extend their shelf life (usually about 3 months).
Not the biggest fan of the rosehip oil from The Ordinary. It just didn't do anything for me. I'm going to eternally chase a product that compares to Sunday Riley's Flora (discontinued) that was rosehip-heavy. Flora is hands-down the best oil I've ever owned. Juno is great, but that's off topic. I haven't tried Trilogy's rosehip oil yet because I'm still trying to force myself to use up what I have from The Ordinary (and the 18 other oils I have), but I will once I can rationalize the redundancy.