Junkyard Tinkerer

With the now region wide AH for commodity's this achievement can be bought fairly easy, if you have a chunk of change.
Once you quested far enough for More Recyling (the bundle thingy in Junkwatt Depot) to be come an infinitly repeatable quest you can combine

• 
  
• 30 Hardened Springs
• 
  
• 5 Machined Gear Assembly
• 
  
• 10 Tempered Plating
• 
  
  

To create a https://www.wowhead.com/item=168946/bundle-of-recyclable-parts] and hand that in at one of the bots.

This gives you a guarenteed https://www.wowhead.com/item=168264/recycling-requisition that contains anywhere between 1 and 220 Spare Parts.
Lets say you average out 100 Spare Parts per box, that gives you 2 crafts of whatever 50 Spare Parts piece you want.
Doing so you would need 500 Recyling Requisitions to go from 0 to 1000.

Now thats all great but nobody was bothering to list these things, but now with the whole region sharing the AH there are more then enough on there.

You would need 15.000 Hardened Springs, 2500 Machined Gear Assembly, 5000 Tempered Plating.
Now thats counting going from 0 to 1k, based on our 100 per box average.
You might luck out and get more, and its unlikely you have to start from 0 crafts, but still.

Based on EU prices right now, the 15k Springs would be 226k, the 2500 Gears would be just over 11k and the Platings would be 9.6k.
But that still 'only' sums up to 245k, and you would never have to farm Spare Parts again.

Its honestly not that bad, and if you dont want to buy all of it you could just weave it in with you farming some stuff yourself to speed it up.

Canned Minnows take 25 scrap and 3 minnows each. This seems to be the most efficient way of getting this achievement, should you choose to grind.

Edit: As of 8.2.5, several recipes have had their ingredients reduced. However, Canned Minnows now cost 50 scrap. This means the only "efficient" way to get this achievement is to craft any of the numerous recipes which cost fifty scrap.

After the 8.2.5 change to Canned Minnows I guess the to go to crafts for Tinkerer is

1. 
   
2. [spell=295290]* for parts.
3. 
   
4. [spell=291600] for cells.
5. 
   

*It's worth noting that any craft requiring 50 parts comes to mind, but grenades are generally the most useful items (15 second non-combat cooldown and packs a punch). You might want to get a stack or two of [spell=294360] and one craft of [spell=300268], [spell=300267] and Orange Spraybot if you still need something from the Crazed Trogg. All other crafts are mostly useless.