Started Methylphenidate today (I believe it's generic Concerta) and I'm not sure what to expect

I'm on 18 mg. My psychiatrist says it takes a week to notice a difference. Unfortunately for me I have to be on a low dose because I have a mood disorder. Unsure if I'll be able to try a mid-range dose in the future though I'm just hoping this medication will give me a boost to help with my focus issues which is important because I'm seeking out my first job. But I guess I'm still confused on what ADHD meds can and can't do. Does it affect executive dysfunction? Or is it more like like a helping hand when used together with coping techniques for it? I heard untreated ADHD can cause depression. I had hopes it will be easier to focus and in turn enjoy my old hobbies.