Inquire about home care methods

I bought a serum containing vitamin C to control blemishes, but when I first applied it, I felt a slight stinging sensation. I'm not sure if this is a normal reaction or if it's not for my skin, so I've temporarily stopped using it. I've heard that it can brown significantly when exposed to air, so I'm careful about how I store it. I'd like to know if I should apply sunscreen more thoroughly during the day or if there are any ingredients I shouldn't use together. Since I chose this product for effective whitening, I'm writing this post to learn about guidelines for safe use without side effects. I've found that applying a moisturizing ampoule before applying it reduces irritation, but I'm concerned that this might reduce the absorption of the vitamin. Could you share your routine on whether it's okay to alternate between vitamin C and other ingredients like retinol, or if it's better to use it every other day? As someone who's just starting to research ingredients for blemish-free skin, I'd appreciate your advice.