Saiki set?

With the full Saiki set you get 150HP, 25PP, and 60 MEL-, RNG-, and TEC-Pwr. Brisa is also an option as a full set will give you 200HP, 20PP, and 70 MEL-, RNG-, and TEC-Pwr.

What about the best augments?

What about Dex and how it effects Critical hits?

@RainGinyu The thing about DEX is that once you have a 7*+ Weapon (except Red series Weapons), its stabilization property is less useful because those Weapons have a bonus to them that makes the difference between your minimum and maximum damage only ~10%, which is higher than most reasonable levels of DEX can get you (you need something like 800+ DEX to match it depending on how much PWR the weapon has).

TL;DR: In general, DEX is not worth investing in if you have a 7* or higher weapon.

Apologies, I asked about augments but it's really item abilities i would like to know about. Does anyone have a resource which show which abilities are best gor hunters?

As a Hunter, you want to look for any Abilites that raise MEL-Pwr, like Might or Quartz Soul. Other than that, you can focus on ones that raise HP or PP.