Gaining spells for the feat ritual caster in AL

Simple enough question(I hope), but I couldn’t seem to find a clear answer anywhere.

This is a Adventure League character. I’ve taken the ritual caster feat on my character, chosen my two spells, but can I then only learn additional spells from other players, or can I spend downtime to learn it from an NPC, if so how are the costs? 2 hours and 50 gold pr. lvl, so a 2nd lvl spell would be half a day and 100 gold?