The [Dera] is where it is today because of three things:

1) Not enough ammo economy
2) This gun will only be useful against Grineer
3) It is only good on Puncture while it doesn't compensate for other damages like Impact or Slash.

Therefore, we are just adding more fuel to the fire by making the [Dera] useful and budget friendly.

For starters, I chose [Fast Hands] because the [Dera] does have a fast reload. So therefore, when running out of ammo, it is more better to prepare for the next shots to be fired rather than taking too long to reload.

[Rifle Aptitude] gives a boost in status chance so that the [Dera] has better odds of leaving Puncture damage.

Now for the last one, there are two options you can choose. For budget players, [Piercing Hit] can be used to boost that Puncture damage. But my suggestion is to use [Piercing Caliber] as that offers four times more than [Piercing Hit] does.