For the first 4 levels of a megadungeon campaign I did gold for XP. Started with a 1:1 ratio, but then realized that was a little too slow, so I bumped it to 1:2.
Once the party achieved 4th level, they had enough gold to stop worrying about paying for things, so I switched to milestone.
I wanted to bring to life the idea that the characters weren’t considered special for the first few levels. If they wanted to become heroes, they’d have to work for it, otherwise they were just seen as weirdos who couldn’t hold down regular jobs.