Up to level 375...
So you are now an Artisan Engineer. Nice. You can make tons of cool stuff and you can't wait to move on up to 300. But wait just a second... Engineering is different than other professions in that at level 225, you can actually choose your specialization.
That's right – you get to start specializing at level 225 instead of 300 or 350. To do so, you need to make up your mind whether you want to go with Goblin Engineering or Gnomish Engineering. Don't know the difference? Well, here is what you need to know:
Goblin Engineering: These players get all of the recipes and plans to make destructive bombs and awesome guns. This will give you a bit of an advantage when you are trying to kill mobs, but you also have a higher chance of hurting yourself or your group if you are not careful. If you want to choose Goblin Engineering, then you need to go to either Tinkmaster Overspark in Ironforge (of course, Alliance only) or Oglethorpe Obnoticus in Booty Bay.
Gnomish Engineering: These players will get all of the cool toys and tricks. These Engineers get to do all of the crowd control and escape artist items, but they are the ones that have all of the cool things that allow them to annoy both mobs and other players! If you want to choose Gnomish Engineering, then you need to go see Tinkerwiz in Ratchet.
And now that you have chosen your specialization, you can get on with leveling your Engineering up to level 300 and beyond!
From level 225 up to level 235: Mithril Casings – You will need to make at least 20 of these and keep them all.
From level 235 up to 245: Hi-Explosive Bombs – You will make 10 of these.
From level 245 up to 250: Mithril Gyro-Shot – You'll make 8 of these.
From level 250 – 260: Dense Blasting Powder – You will need to make 25 of these and keep all of them for later.
From level 260 – 290: Thorium Widget – You will make 30 of these and you need to keep them all.
From level 290 – 300: Thorium Tubes – You need to make 10 of these and you need to keep them all as well.
Once you reach level 300, then you can train for Master Engineering. Alliance players will go to Lebowski in Honor Hold, Hellfire Peninsula and Horde players will go to Zebig in Thrallmar, Hellfire Peninsula.
From level 300 – 310: NOTE: here you'll make three different things:
Fel Iron Casings – You'll make 40 of these and keep them all.
Handful of Fel Iron Bolts – You'll make 60 and keep them all.
Elemental Blasting Powder – You'll make 45 of these and keep them all as well.
From level 310 up to level 320: Fel Iron Bombs – You'll make 10 of these.
From level 320 up to level 335: Fel Iron Muskets – You'll make around 15 of these.
From level 335 up to 350: White Smoke Flares – You'll make about 25 of these.
From level 350 up to 355: Felsteel Stablaizers – You'll make 5 of them.
From level 355 up to 360: Ultra-Spectropic Detection Goggles – You'll make 5 of them.
From level 360 up to 375: Khorium Scopes – You'll make 15 of these.
And there you have it – you are now level 375 in Engineering. Now, there are tons of other plans that you can make – this is just the cheapest way to get you there. Good luck.