Proficiencies to Stat Building provide the basic traits useful to any build, from Ability Score increases to Saving Proficiencies. It includes other traits for some slightly more narrowed builds, such as Magic Adept and Skill Proficiencies.
For those looking to boost their skill bonuses, check out the Insight to Skills which gives a full list of useful traits.
Your Protection, from AC to Saves has a range of traits dedicated to boosted those character facets of AC, Damage Reduction, Saves, Immunities and Resistances. Note, many of those listed are Fortifications or Immunizations.
Additions to Attacks is a general and large category that has traits for increasing damage output, changing damage types, and dealing better critical hits.
For traits that protect against or inflict conditions, read through the All About Conditions page. This also includes traits involving common battle actions.