One time lump of 74k Runes for leveling and 5 Dragon Hearts.
Go to Fort Faroth in East Caelid. You can run there pretty much just after starting the game. You need a bleed weapon or access to Blood Grease to add bleed to your weapon.
After making it to Fort Faroth, attack the tail of the dragon until it dies to bleed. This should take a few minutes and you can also poison it for added damage. If you have friends, summon them and let them summon you for the kill. Everyone gets the full 74k Runes and the host gets the additional 5 Dragon Hearts.
Early Bleed Weapon Reduvia
The earliest bleed weapon is the Reduvia and is dropped by the NPC invader Bloody Hunter Nerijus just outside the Murkwater Cave.
You can also use bleed grease if Nerijus is too difficult for you to beat. The bleed grease recipe can be found in a chest in the room at the top of the main stairs of Fort Haight.