Jetpack Joyride is a nice game, but it can be tedious due to its slow growth rate. You will need to repeat the same levels over and over to unlock new gear. There's no legal way to cheat in Jetpack Joyride, but still there many tips to help you to progress faster in the game.
The coins recovered during a ride can be used as currency to buy various gadgets and upgrades. You must therefore focus on objects that will help you collect coins faster, such as the magnet....
Jetpack Joyride allows you to combine your gadgets to create new ones. If you want a list of all the combinations, it is available on the internet.
Similarly, if you want to get a preview of the prices in the game, there are several websites that have drawn up comprehensive catalogue with descriptions and specifications about each items.