For my West Marches game, I've changed how xp is accumulated. It goes like this:
When the PCs return to 'civilisation', they earn 1 xp for every 1 gp (or it's equivalent in value) that they have acquired from treasure hunting.
Killing monsters and enemies only earns PCs 10% of its actual xp value. - Thus a goblin will only the party 5 xp instead of 50.
This is meant to reward players for exploration and the accumulation of wealth - which are important themes in a West Marches style game.
Combat is meant to be a bit more dangerous and less rewarding - to force the players to consider the consequences of their decisions more often.
At the end of the first session, they had earned 84 xp in total: 59 xp from treasure and 25 from combat. That feels a little low to me? By the normal rules, they would be at 250 xp and nearly level 2. I believe one of the design decisions behind 5th edition was to have PCs advance through the first 3 or so levels very quickly. Perhaps they should be advancing quicker? Maybe I should give out more treasure or more xp for combat?
The players seemed OK with it, but I'll see how it goes.