Contessa is a defensive swashbuckler companion. In PvP its best to give her first strike 3 to combo with Gallant Defense to all but neutralize swashbucklers' black fog since first strike 3 "unhides" hidden units before they attack.

In general, if a companion has multiple guaranteed attacks (say a super strike and a Buccaneer's strike) or a 2X movement attack (Vicious Charge) it's best to give them Relentless 2-3, Bladestorm 2-3, and just fill in the rest of the talents. If they come with some sort of method to protect themselves or your team (Triton's Song, Gallant Defense), give them defensive talents like first strike 3, htl 3, etc.

If you have any questions regarding specific companions' setups, feel free to reply to this thread with the companion in question.

ricemann on Jul 17, 2017 wrote:

Here's a giant question... HOW DO I BUILD COMPANIONS??
Like seriously, i don't understand it.

I get that some companions are offensive, and you give them burst fire/relentless
I get that some companions are defensive, and you give them hold the line and repel borders
I get that some companions are specialized, and they have unique epics

But apparently, you're supposed to give Contessa first strike 3?!??!? WHY????
I don't understand why you would do that?

Can somebody please explain some of the logic behind companion builds. I want to create them for myself confidently without thinking im ruining my companions with lack of knowledge.

-ricemann

Contessa is a swashbuckler, with FS3 she can keep hitting those opponents with Vengeance Strike. Also FS3 is useful in PVP as this talent ( at 3 ranks ) removes hides.
Basically by class:
Swashbucklers benefit from Agility & Dodge, giving them First Strike & Riposte is a must.
Buccaneers benefit from Tough, Strength & Armor, these are basic "tanky" options. Ratbeard is an exception to this rule as he doesn't get Vengeance Strike, giving him Repel Boards & Hold the Line is a really good idea.
Privateers benefit by giving them as much Will as you can, dodge wouldn't hurt either.
Musketeers benefit from Agility & dodge for them is a good idea, because they don't get much armor or health.
Witchdoctors, give them Will and Spirited.
I hope this gives you a basic idea, but I believe that Central has guides that you can look at.