In the old Testament, the law had a series of provisions to provide for worship and for those who were poor. One of them was tithing. You were to give a tenth of your crops — and by extension your income — to the temple.
There were other parts of this that most people ignore. Every 50 years all debts were to be forgiven, and all land return to the original owners. (Buyng farmland was in fact a lease of the land until the Jubilee). Debtors could indenture themselves to relieve debt. There were specail tithes for those with no incomes.
But the old covenant has gone. Paul, who knew the law, advised us this way
1Now concerning the collection for the saints: you should follow the directions I gave to the churches of Galatia. 2On the first day of every week, each of you is to put aside and save whatever extra you earn, so that collections need not be taken when I come. 3And when I arrive, I will send any whom you approve with letters to take your gift to Jerusalem. 4If it seems advisable that I should go also, they will accompany me.
Paul is preaching generosity. He is not giving them a percentage. I think one should give generously, after providing for your family… from dealing with their debts to getting them what they need.
Tithing is not Pauline. It is part of prosperity gospel — seen as a cause of blessing, as if God is a collection box or a one-armed bandit that we can manipulate. He is sovereign.