Dragons are worth fighting for their hearts which unlock special incantations at communion altars, each dragon giving something unique for spellcasters. Going after big ones like fortissax and placidusax gets you remembrances, trade those in for special gear like that sweet cragblade that everyone wants. Some dragons are guarding really important areas especially in liurnia, so you'll need to clear them anyway to progress and explore properly.

Might be interesting that taking down specific ones like gransax gets you legendary weapons needed for achievements, plus theres some good story bits about godwyn if you're into the lore. Getting those dragon communion spells early makes a huge difference, just remember some dragons hit way harder than they look so maybe grab decent equipment first. For real though those breath attacks you get from their hearts are absolutely worth the trouble especially early game