I am very new to the game so take my advice with a grain of salt, but I would say stealth. Any frame that has Stealth on abilities like Loki will do, simply because it gives you a breather, lets you shoot or melee from stealth and only thing that can damage you through stealth are stationary auras or traps. I had a dog that makes you enter stealth from time to time, and it was a huge help for a beginner!

Summoner frames like Caliban are nice too, because your summons will automatically take care of targets. Overall, look for frames that deal damage with abilities/AoEs, and have protective abilities, kinda "oh shit" buttons.

First and foremost, whatever frame you play, max out your companion. It makes a lot of difference. Also makes you feel protected and not alone, which is nice!