You can earn Crowns through Quests, Achievements, PvP and Sieges.
If you're just starting out, get the homeland quests from your adviser and complete those. Also, do a few of the easy achievements like Gregarious (add a friend) or Book Worm (use in-game help).
You can also exchange Gold for Crowns. So mine, trade resources, and raise livestock (sheep/unicorns) to boost your Gold reserves and use that to get some Crowns.
And while your friends can't send you Crowns, they can send you Gold (and other resources).