Warhammer: Vermintide 2

A bit of good news on this achievement -- upgrading equipment also counts as "crafting" an item and adds for the total for this achievement (as you get a new piece of equipment upon doing so), so this won't take as long as you would think.

To craft, first you need materials, which means you need to break down old equipment pieces in your inventory via the "Salvage Items" option in the Crafting Panel. Salvaging will always return Scrap, Salvaged Weapon Parts (if you scrap a melee or ranged weapon) or Salvaged Gemcutter's Toolkits (if you scrap a necklace, charm, or trinket), and Dust corresponding to the rarity of the salvaged equipment (except for white equipment).

Now that you have materials, on to crafting -- as you level up each Hero, you'll earn Blacksmith templates which can be used to craft the corresponding equipment of random rarity (except for Red quality items). Crafting new equipment costs 10 Scrap and either a Salvaged Weapon Part or Salvaged Gemcutter's Toolkit depending on what you're trying to make.

You also have the option of not using a template at all (if you want to start REALLY early), and you'll receive a random piece of equipment.

After crafting a weapon (or finding one you'd like to upgrade). You can then upgrade items up to level Red to add to your crafting total:

White to Green costs 20 Scrap
Green to Blue costs 30 Scrap
Blue to Orange costs 50 Scrap
Orange to Red costs 5 Bright Dust (which you get from breaking down a red item, so yea, you won't be doing this level for a long, long time)

So, crafting a white item, then upgrading it to orange will add 4 ticks onto the achievement progress. Crafting a green and raising it to orange will add 3 ticks, etc.

Since you'll be moving up in equipment power quickly in this game (and as each completed level drops three pieces of equipment), you'll be scrapping lots and lots of items, so you'll easily have a large pool of materials to craft with. This goes double if you're doing daily challenges, as these give you extra crates, and thus extra equipment to scrap, so I recommend doing these as often as possible to add to this achievement.

One final word: I got this achievement without really trying for it just before my first character hit max level 30 as I would craft him (Bardin) new Drakefire Pistols every few levels (most of the other dwarf ranged options are bad for Ironbreakers, so I liked having these on-hand at all times).

Alternatively, you can just wait until you hit item level 300 (max), then craft Orange melee and Orange range weapons for all your characters. This will get you the achievement (or really close to it) in one quick shot.

EDIT July 8th, 2019: According to iMaginaryy, re-rolling properties on gear (and I'm guessing by extension traits as well) also counts toward this achievement. This is really nice as re-rolling properties is cheaper than creating new gear wholesale, in case you want to get this achievement as fast as possible. I however find that re-rolling properties on early gear to be long-term unhelpful as you tend to abandon gear quickly upon leveling up. So, you can wait and get the achievement naturally and save some crafting mats or you can speed up the process by re-rolling properties (and helping yourself out in the short-term). In other words, you have a lot of good options...