If you're looking to buy a home Fishtown or lower Kensington is your best bet, everywhere else that's a livable neighborhood is way too expensive. If you're renting then just about anywhere is an option, especially if you won't have a car. Don't bother looking in Northeast Philly, it's either hood or lame residential area and feels really disconnected from the rest of the city.
Anywhere worth going in Philly is essentially within a 5 mile radius, you can skate to just about anywhere, and the subway is decent. Been here 7 years and I love it.