On the Ethereum blockchain, gas refers to the cost necessary to perform a transaction.

And gas limit refers to the maximum amount of gas that a user is willing to spend on a particular transaction.

Ethereum sender pays transaction fee based on his/her gas price and actual gas usage not exceeding provided gas limit.

Providing less gas limit than actual gas usage will cause transaction failure.

Source: https://www.investopedia.com/terms/g/gas-ethereum.asp

A gas limit of 300,000 seems enough for almost all Asinerum-based tasks.

A gas limit of 21,000 is required for a simple ether sending, with no additional data.

Note that you are going to pay ether for only actual gas usage.