My priority is to work my way through the GEDCOM tree I initially imported, clean up the entries I haven't already, and add or link by hand the siblings and cousins and other collateral lines that weren't in that initial import.
In the process, I'm running across various people of the same names with minimal data; where I can find good data, I'm adding information and sources to those records so they don't show up as potential matches when they're 150 years off or born on a different continent.
(And when I get bored and want to do something completely different, I sort the surname UNKNOWN by date, scroll through to the 1800s, and look on Family Search to see if I can find marriage records and supporting data to put family names on them.)