Engineering is the best combined with Mining because you can farm most of the needed materials, and you will save a lot of gold.
If you are low on gold, I recommend you to try this Gold Making Guide, it can help you to make loads of gold.
If you are still leveling your character or you just started a new alt, I recommend you to use a leveling guide. You can level your character to level 120 in 8 days with this guide.
Learning Legion Engineering
First, visit your Engineering trainer Timofey Oshenko
The quest reward is [Legion Engineer].
Most Engineering recipes are unlocked by doing quests. These quests are given by one of the NPCs around your trainer.
There are 29 Engineering quest in total, they are pretty straight forward, so I will not write down the details of every quest. Some of the quests lead you to dungeons but you can finish every quest easily in a few hours if you start them at 110, otherwise, you will have to wait because later quests have a level requirements.
You don't have to do every Engineering quest to reach 100, but you must complete All Charged Up. (Around 10th quest in the chain)
Most Legion recipes now have 3 ranks. Higher rank recipes allow you to craft an item for fewer materials, and higher rank recipes give skill points longer. Therefore, you should only use rank 3 recipes when you can.
Rank 3 recipes come from different sources like Vendors, World Quests, Reputation, dungeon drops, and even rated battleground win.
If you hover over the little stars in your spellbook, you can see the source of the next rank for the selected recipe.
1 - 100
You basically have to make the following recipe around 140 times:
- 140 x [Rank 3 - Gunpowder Charge] - 140 x Leystone Ore, 2800 x Oversized Blasting Cap
Make sure to get the RANK 3 recipe! Higher rank recipes give skill points longer.
2800 x Oversized Blasting Cap cost around 3200 gold, but you might need to make more from these because this recipe will be green between 90-100. Buy these with shift+left mouse click.
Gnome characters have +15 Engineering skill because of their passive [Engineering Specialization]. An extra 15 Engineering skill means recipes stay orange for 15 more points, so you have to make a lot fewer of these.
Rank 1 recipe
You already have rank 1 if you finished every Engineering quest. It was a reward from All Charged Up. (you have to start doing your Engineering quest until you get to this one)
Rank 2 and 3 recipe
The Rank 2 and Rank 3 is sold by The Widow for 250, and 500 Sightless Eye at the Dalaran Sewers. You can get 750 Sightless Eye in about 30 minutes, or even less. Visit my Sightless Eye farming guide if you don't know how to get them.
I hope you liked this Legion Engineering leveling guide, congratulations on reaching 100!