Gas Optimizations

[code423n4]

For loop optimization

for(uint256 i; i < length; ){
...
unchecked{ ++i; }
}

contracts/ForgottenRunesWarriorsMinter.sol:162:        for (uint256 i = 0; i < numWarriors; i++) {
contracts/ForgottenRunesWarriorsMinter.sol:220:        for (uint256 i = 0; i < numWarriors; i++) {
contracts/ForgottenRunesWarriorsMinter.sol:259:        for (uint256 i = 0; i < count; i++) {
contracts/ForgottenRunesWarriorsMinter.sol:355:        for (uint256 i = startIdx; i < endIdx + 1; i++) {

> 0 is less efficient than != 0 for uint in require condition

Ref: https://twitter.com/GalloDaSballo/status/1485430908165443590

https://github.com/code-423n4/2022-05-runes/blob/060b4f82b79c8308fe65674a39a07c44fa586cd3/contracts/ForgottenRunesWarriorsMinter.sol#L140-L143

        require(
            numWarriors > 0 && numWarriors <= 20,
            'You can summon no more than 20 Warriors at a time'
        );

https://github.com/code-423n4/2022-05-runes/blob/060b4f82b79c8308fe65674a39a07c44fa586cd3/contracts/ForgottenRunesWarriorsMinter.sol#L210-L213

        require(
            numWarriors > 0 && numWarriors <= 20,
            'You can summon no more than 20 Warriors at a time'
        );

Use custom errors

Solidity ^0.8.4 allow the use of custom errors to optimize gas usage.
https://blog.soliditylang.org/2021/04/21/custom-errors/