When one gains rudimentary prayers(ta) what tier of spell does that person gain?

Tier 1.

Pretty sure its a Tier 1 spell.

Yup, Tier I.

since no one is quoting source, that was erattaed specifically to only include Tier one spells, and you should be able to find that in the forthcoming eratta

As said in prior posts, rudimentary prayers is a tier 1 spell.

Afterwards, you can either take Divine Spell Casting if you meet the other requirements or use Learn Spell to learn more spells. Learn Spell's only requirements for learning 1 additional spell is that your character's tier is high enough and you know already know 1 spell from its tradition. Basically, a Martial character that gets access to Rudimentary Prayers can at a later tier pick up select spells from the same tradition.