Dead Space 3

The most time consuming part of this achievement is collecting the 8 circuits. Everything will come easily by natural progression. However, there is a way to speed up the circuit collecting process. And that is simply to check your checkpoints. Every time you get a checkpoint, check your surroundings, if there is a circuit box on the wall somewhere nearby, you are in luck. Collect, the circuit, and save and quit. When you go back into the game, you will still have your circuit, and there will be a new circuit in the box waiting for you. Simply rinse and repeat, then slap all of your brand new circuits onto your weapon.
As for the attachments; The easiest attachment for slot one is the scope. It takes almost no resources, so it is easy to craft. As for slot 2, electrical charge I found was the easiest to craft.
If you have the preorder weapons, then the tools and tips on the evangelizer will already be filled out, so you only need the two attachments, and the circuits.
If you do not have the preorder weapons, then wait until around chapter 6. At this point, you will have more than enough resources to craft all necessary materials, and even with light exploration will have found enough parts to complete your weapon.

EDIT: As stated by ZombieShellHead, if you played DS2, you will start out with the Planet Cracker Plasma Cutter, and that is also an easy weapon to max out.

For a weapon, you can create a bottom tool and top tool. Add these both. Look around or use guides for circuit boxes to find circuits. You can also get some from enemies. You need 8 of those. You'll easily get 8. If you look at your circuits at the Bench, you'll see different ones like "+2 damage, +1 rate of fire". Attachments take a small number of resources to craft and can be found on enemies as well. Resource bots can be used to obtain a variety of different types supplies if you need them. You need two attachments and two tips. Tips are little tools you put at the tip of a weapon to change the way in which their projectiles behave. Once your weapon has 2 tools, 2 tips, and 2 attachments with all Circuit slots filled, you'll get this achievement.