Double XP and Health Replenish : You can change the date on your PC while playing the game to refill your health instead of waiting. At the same time you may be granted double XP - A light blue highlight over the experience bar means the double XP effect is in place. The effect last up to 8,000 gained experience. You can change the date again to replenish the effect.
Once you've completed tutorial, you should start the following quests.
( See the first video for reference)
1. Save the Princess - Oregon Pass - Assassin's Creek
2. Malanoche Assault - Arizona
Other fast quest:
3. Pond Dungeon Oregon Pass
4. Gates of Hell - Oregon Pass - Sister's Ingrid Mines
The top 2 are the best options for one particular reason. You may run into the invincibility glitch during those two quests. This will make leveling up easier for you. I do not know the exact cause for this glitch to occur but throughout my play through I noticed several factors that can increase that chance.
1. Lag- Playing music, watching movies, etc.
2. Complete the mission as fast as you can , defeating any enemies at first sight
3. Consistently shooting/moving/rolling
Note: Using the map travel , sign post, or changing region (Arizona to Oregon - vice versa ) will end the invincibility effect. Make sure you travel by foot or horse.
Watch the videos - The invincibility effect can occur during or start of the mission. In my case the latter occurred.
Once you reach level 10 and have 5k coins buy the Revolver sniper immediately and start the Eagle-Eye mission. **If you are inexperienced with the sniper rifle , I suggest you first practice "The Outlaw Hunter" mission at Assassin's Creek.***
USE coins to upgrade your sniper along the way. DO NOT use any stars until you unlocked all tiers that cost coins. Farm Eagle-Eye mission until you reach level 35 and accumulate 500k coins for the Gatling Annihilator. I have to emphasize this but the Gatling Annihilator will SAVE you a lot of time so its best to get this weapon as soon as possible before going through the other missions.
See the demon hunter IV guide for more information for farming Eagle-Eye.