Mental illness and the Layperson's Practice

I would like to return to the practice of Buddhism. Where should I begin? I have a serious mental illness. It has been well treated by medication. When I was young, before I developed this illness I would practice meditation as best I could. But I had no mentor and so I don't know if my practice was correct. I do not come from a Buddhist culture so I know little about the subject other than what I have been able to read. Will my medication interfere with meditation as it is obviously mind altering? Should I start for example with meditation on impermanence, on mindfulness, or by attempting to reduce my desire?