Gas Optimizations:

I. Use Custom Errors instead of Require Statements

The benefit of using Custom Errors is that they significantly reduce gas costs especially deployment costs because unlike require, Custom Errors do not store a dynamic string of Error Message to revert when an operation fails.

Examlple: Execution Cost: 232904

contract Ownable {
  
    address public owner = msg.sender;

    // `require` Not Optimized:
    function newOwner(address _newOwner) public {
        require(owner == msg.sender, "Only Owner Allowed");
        owner = _newOwner;
    }
}

Examlple: Execution Cost: 232904

error Only_Owner_Allowed(); //Custom errors are defined using the error statement

contract Ownable_SmardWay {
  
    address public owner = msg.sender;

    // `Custom Error` Gas Optimized:
    function newOwner_SmardWay(address _newOwner) public {
        if(owner != msg.sender) { revert Only_Owner_Allowed(); }
        owner = _newOwner;
    }
}

References: https://tinyurl.com/3yaj4u8n & https://tinyurl.com/2k3wv67m

II. Use ++i instead i++ inside loops

++i returns the incremented value, i++ returns the non-incremented value, which costs a little bit extra gas.

Examlple: Execution Cost: 182005

contract PrimeCheck {
    function primeChecker(uint n) public pure returns (bool) {
        for (uint i = 2; i < n; i++) {
            if (n % i == 0) {
                return true;
            }
        }
        return false;
    }
}

Examlple: Execution Cost: 181573

contract PrimeCheck_SmardWay {
    function primeChecker_SmardWay(uint n) public pure returns (bool) {
        for (uint i = 2; i < n; ++i) {
            if (n % i == 0) {
                return true;
            }
        }
        return false;
    }
}

References: https://tinyurl.com/mr4b4jcd & https://tinyurl.com/mr2xtn2r