You will come across many monsters (which can take one or two shots to kill, or a single bounce), bear traps (which can be avoided at the last second but requires good timing to do so) and the regular black holes (shown as paint).
As you go further on the game, you will see more coins on coin packs. Here's the list of known coin pack bonuses:
At the beginning of the game, all coin packs only give one coin.
At 15000 points, all coin packs give two coins.
At 25000 points, all coin packs give three coins.
The Shop Edit
The Sumo outfit: Costs 3500 coins and enables the Doodler to stomp and shake monsters down.
Shadow outfit: Costs 2500 coins and makes the Doodler invisible to monsters.
Double Jumper: Costs 6000 coins and makes the Doodler jump once, and jump high a second time.
Sugegasa: Costs 4500 coins and makes the Doodler turn upside down and bounce extremely high
Head Start Cannon: Costs 250 coins each and gives Doodler a headstart at the beginning of the game by shooting Doodler out of a cannon.
Resurrect Barrel: Costs 500 for 5 and saves Doodler when it falls.
Propeller hat: Costs 250 coins and flies Doodler higher than regular propeller hat. It can then be further upgraded up to the carbon propeller hat. Each upgrade increases its flight time.
Jetpack: Costs 500 coins and flies higher than regular jetpack. Multiple upgrades can be bought later on to improve the jetpacks power ending with the super sonic Jetpack. Each upgrade increases its flight time