[Nether_Ruler]

Since you only started 5 months ago, I have a few questions first. Are you on a main road? If not, put some signs on the main road (come to _____ furniture store for all your furniture needs!) if you are on a main road, still put those signs around (Not on private property :p) and direct them to your store.
And on the billboard thing, so long as it's in the general area of your store, I think you should be fine. It really should be that far away as people don't really like to travel long distances for stores xP