It's simple - buy a plant. Plants in your home help to give you clean air, naturally. Not only that, but caring for a plant can help to make you feel better. The act of caring for something is good for your mental health and for your physical health. Puttering around with it can help you relax. While a plant can't play with you like a pet can, it does need you to keep it healthy, and being needed is a good thing!
Now, I definately do not have an indoor plant green thumb, but there are a few plants out there that people like me can succeed with. Ivy type plants are usually easy - I love one called Pothos - I've had many in my life and they've lived long and well. I still have some of them. My sister, who frequently forgets to water the ones on top of her cupboards, still has the same ones, too. Once she tried to kill mine when I moved away (OK, not on purpose, but still) and I managed to save it from near death. You can take cuttings and put them in water to root and them plant them, thus expanding your collection at no cost. This particular plant is amazing as lives just about anywhere and comes in pretty varieties, too.The website below shows the varieties.
You can pot your chosen plant in organic soil, feed it regulary with organic fertilizer and you'll have a healthy green addition to your home, that gives you the benefit of clean air at the same time.