The second level tattoo Ancestral Geometry reads as follows:
Geometric precision and perfect angles signify that an artist with exemplary knowledge of dwarven tattooing traditions created this body
art. Your family's ancestral stories, recited throughout the tattooing
process, bind your blood even tighter to theirs. During your daily
preparations, you manifest a visitation by an ancestor—possibly via a
dream, a vision, or a magical trinket left by your bedroll. Roll 2d20
and record the highest result. Then roll 1d6 and note a type of saving
throw: 1–2 Fortitude, 3–4 Reflex, and 5–6 Will.In addition, until the next visitation, you gain a +1 item bonus to one Lore skill related to the ancestor, as determined by the GM.
Usually, the ancestor provides a kind of knowledge they believe you'll
need. For dwarven ancestors, the Lore skill is usually Architecture
Lore, Engineering Lore, Genealogy Lore, Labor Lore, Mining Lore,
Warfare Lore, or Lore about a dwarven deity.Activate (Reaction) envision (fortune); Frequency once per day;
Trigger You rolled a saving throw of the noted type; Effect Replace
the roll with the d20 roll from your ancestor's visitation.
I'm unsure how to properly implement the second paragraph. My character happens to be a kobold trained in Kobold Lore. If the GM knows our party is likely to encounter kobolds during the upcoming day, I assume they would give that lore skill a temporary +1 item bonus until my next daily preparations. What about a lore skill that my character does not possess but would make thematic sense for my ancestry like Trap Lore or Dragon Lore? Do I temporarily gain that lore skill with a bonus of my intelligence modifier +1 with no proficiency? What other lore skills would be reasonable for a kobold? I assume anything listed in the ancestry entry in the APG?
Typical kobold backgrounds include artisan, artist, criminal, hunter, miner, scout, and tinker from the Core Rulebook, plus bandit, cultist, scavenger, and servant from this book.
Best Answer
You Don't Get Free Proficiency
The Ancestral Geometry tattoo does give you a (GM-determined) variable +1 to a Lore skill, but never mentions that it gives you any proficiency. So if you are untrained in the Lore skill, you would use: untrained proficiency plus your Intelligence modifier plus any bonuses (minus any penalties). If you have 14 Intelligence, and a +1 item bonus to Lore (Sewers), but were untrained, you'd simply have a +3 to Lore (Sewers) checks.
How To Make This Better
Since there are an infinite amount of Lore skills, you have a few options to try making this better:
Some recommended Lores
You touched on a good place to find relevant Lore skills for kobolds. Here are seven recommendations to align with the 7 ones provided for dwarves - by no means is any GM restricted to this list, nor is it exhaustive. They are all from the Common Lore Subcategories though, and so should both be fair and potentially come up in pre-written adventures.