Apps depends on your personal usage/taste. For photography you may use, Snapspeed, Photoshop for phone, instagram etc you can either install those from playstore or you may download the apks using torrents or from Mobilism and blackmarket.
For GPS/navigation, 1.Sygic for Offline house to house navigation. (no internet needed after initial setup)
2. Mytracks for milegage calculations and tracking etc.
3. Google Maps for Sat Nav. etc ( but sygic is way better in terms of route calculations etc Personally I don't use this much)