The verb ir with gerundio forms the expression for gradually. Some of the expressions would also be translated with to be beginning to.

Se iba poniendo pesado. Se va poniendo pesado. El dinero se nos iba agotando.

Gradually he became a nuisance. / He was beginning to be a nuisance. Gradually he becomes a nuisance. / He is beginning to be a nuisance. Gradually we were running out of money. / Gradually the money was used up.

The alternative would be to say bit by bit = poco a poco

Poco a poco se nos agotaba el dinero.

Bit by bit we were running out of money. (exact translated: Bit by bit the money was used up.)