Offering is a physical practice with spiritual significance. It is not something that should be done without understanding. How much it should be depends on your presumed self-status.
Offering is the token of our presence in the presence of God and should be according to your status (according to the blessing of God in your life). The footprint of an elephant is bigger than that of a sheep (to whom much is given, much is expected).
Some will say if you do not have, it is alright! That is another wrong teaching. Coming to the presence of God without a token is like not coming at all (Deuteronomy 16: 16-17). The least you come with is widow’s might. It is better to always give one penny as regular offering than to give one pound today and have nothing to give tomorrow
The wisdom goes thus.
How much do you think you can afford monthly (2 Corinthian 9:7)? Divide it by the number of times you go for church services and be faithful with it because it is not right to appear before God empty handed.
Subsequently increase this gradually as your financial capability increases