Thanks for trying out my game and glad to hear that you are enjoying it!
Good to hear that you figured out how the tricks work. As for the boost, after having unlocking it you gain one gauge of boost which filles up after performing a trick and landing it (having a higher multiplier give you more charge). When the gauge is full it will be filled white and there would be an outline around it. If you don't use the boost, after a few seconds the gauge will start flashing followed by the gauge being depleted. So to keep the gauge fully charged you need to keep doing tricks and landing them. When the gauge is full you can double press A to use the boost, giving the player a speed boost to get the player out of tricky situations.
Hope this clarifies it.
And again thanks for tyring out my game :)