One idea is to think of your keywords as questions that searchers are asking--and then use your site to answer them. So, a search for "tub cleaning supplies" might stem from "where can I get tub cleaning supplies in Carson City?" Your Web site, offering tub cleaning supplies online, as well as the directions, contact info and hours of operation of the store in Carson City, answers that question.
Secondly, expanding your keyword list isn't always the best strategy. If you're selling tub cleaning supplies, bidding on "bathroom cleaning supplies" might be a good thing, but "household cleaning supplies" might not--as it would dilute your budget and bring in less-qualified traffic.