No Forma, No Catalyst, Minimal Endo

This build is written by a newbie, for newbies, and it's so cheap it's practically free. It doesn't have much survivability though, so expect to see it dead most of the time on higher level missions.

With this build, your companion will:

• automatically open and loot any breakable loot containers and resources nearby,
• increase your max ammo
• convert useless ammo into the type you need, and
• provide loot and [Enemy Radar] range.

Keep an eye on the minimap not only to see where enemies are, but to look for loot that your [Carrier] doesn't pick up with [Vacuum]. It cannot pick up the very valuable Ayatan treasures that can be traded for a good amount of endo.

I'm a newbie and this sounds great! How do I get these things?

Building a [Carrier] companion
Go to the main menu, go to Market, and buy the blueprint for 100,000 credits. If this sounds like a lot of credit to you, just do a few dark sector defense missions. Seimani on Ceres is my personal recommendation for newbies as its reward is higher than the next few sectors after it for some reason.

Mods
[Vacuum], [Ammo Case]: You get these for free when you build [Carrier].

[Calculated Redirection], [Regen]: Charger (corrupted monster). While the drop rate for these is rather low (about 1 in 200), these enemies are so common you'll have multiples of these mods before you know it. To lower the endo cost and keep the capacity low enough that you don't need to use a catalyst, don't bother leveling [Regen] and keep [Calculated Redirection] a couple of levels below maximum.

Animal Instinct: Nightmare mode missions. Unlock these by clearing all locations on a planet/sector, then choosing the mission with the red swirl. This mod typically drops from nightmare mode missions on Uranus, Neptune, Pluto, Eris, or Sedna. If you haven't gotten that far in the star chart, it can also drop from any nightmare mode rescue mission, as long as you can kill every warden and rescue the captive without triggering the countdown timer.

[Looter]: Cephalon Simaris. Visit him via fast travel in any relay, and do a few days worth of daily synthesis quests to earn the 75,000 standing needed to buy this mod. You'll also earn some endo while doing so.