A 20* is (usually) the best choice for a first quilt. If you already have one, though, that runs around 30*, I'd think the 20* is too close to it, unless you're really going with something to save space/weight. If that's less of an issue, I'd personally go with the 0*, or perhaps at the most, a 20* with 2-3 ounces of overstuff to bring you down to around 10.
Father. Husband. Scoutmaster.