Each turn, a player would have a limited amount of action points they can use to perform actions. Each action would cost a specific amount of points. If you don't have enough points, you can't do the action.
The player can see how many action points they have at any time.
In the rules...
You can enable or disable the mechanic.
You can manually set each of the actions' cost in action points.
You can set how many action points a player gets at the start of each turn: constant, or linearly dependent on province count.
You can set if excess actions points are brought over on the next turn.
Each turn, a player would have a limited amount of action points they can use to perform actions. Each action would cost a specific amount of points. If you don't have enough points, you can't do the action. The player can see how many action points they have at any time.
In the rules...