Put your device on airplane mode to limit the number of ads that appear.

Keep in mind laying in airplane mode also means that you can't watch video ads, which are one of the best ways to gather coins.

You can purchase a variety of extra characters. Most of them are available in mystery boxes, which you must spend 50 coins to open. Keep in mind that the characters you obtain from the mystery boxes do nothing more than affect cosmetic appearance.

As for dragons, you can only purchase them using real-world money.

You can also gain some characters by downloading other games from the same developer (look for download links below the characters that are available using this method).

You can give yourself a better chance by carefully timing your jumps and showing patience. After you jump, you shouldn't jump again until the character lands.