This game has not been updated in quite a while, but this is one of my go to games. You can do in app purchases to speed up the process, but you can accomplish pretty much everything without doing any in app purchases.
Hill Climb – Dirt Master 3D is a hill climb offroad Racing game with breathtaking 3D graphics and addictive gameplay features. Push the pedal to metal, earn coins and stars, complete main goal for extras, upgrade your vehicle, beat opponents’ record time.
– More than 800 levels with various environments and up and down hills
– 13 different vehicles: Buggy, Jeep, Hot Rod, Military Jeep, Tractor, Monster Trucks, Van, Truck, Futuristic, APC, Motorcycle, Golf Car
– 16 different game modes: Hill Climb, Fuel Madness, Gentle Push, Time Trial, Football, Balloon Collector, Volcano Eruption, Rocket Hunter, Pack Delivery, Mine Field, Log Survivor, Balloon Finder, Golf Ball Thunderstorm, Time Chaser, Ring Hunter and Butterfly Catch
– 5 various stages: Forest, Mountain, Canyon, Vulcan and Snowy
– Breathtaking 3D graphics
– Accurate and realistic physics
Plenty of game modes also. This game is a great game to have on your device.