fastest way to get xp early in a new survival world?

villagers, if you find a village early. every trade gives xp, and once you've got a librarian selling mending your tools stop wearing out as well.

honestly coal and lapis while you're branch mining, and cook everything in a furnace since the xp builds up in it until you take the output out. breeding animals gives a bit too. the real jump is finding a zombie or skeleton spawner in a dungeon and building a quick trap around it. that'll carry you to enchanting way faster than anything else early on.