Certain restrictions are applied to Raids in the game. These are as follows:
You may only gain a net total of 500,000 Resources each day from other players. This limit includes both Resources gained from successful Raids and those sent to you willfully by allies. This maximum is a net figure, meaning that if another Commander raids Resources from you, these are deducted from your net gain.
There is also a 7-day cap of 50,000 Resources that can be gained from each Base. The seven days in question begin immediately after the first Raid. On the 8th day, you can raid the same amount of Resources you raided the first day, so the rolling 50,000-Resource balance is kept constant. This limit is a net total and also includes both Resources gained from successful Raids and those sent to you willfully.
Each player initially has 20 Raid Attempts per day. The number of attempts you have left is shown on the "Raid" button when you tap on a Base via the Map. It is possible to increase the amount of daily Raids available to you by activating your Elite Status, which reduces the amount of time you have to wait between Raid attempts.