Branch out of clearance. Seriously. Clearance is the lowest of the low hanging fruit. Not only does it get hit by every seller in the area meaning you better be quick, it also tends to get saturated with sellers so prices drop. What that means is if you are tight on funds you end up selling for little to no profit or if your funds aren't tight you have to wait out the low priced sellers.
Go to areas of the store you wouldn't think of and scan. If you are brand new with no categories ungated you will be looking in the most heavily competitive areas but you gotta start somewhere.