Hello! I suppose there's a spell missing in the drop-down for Ritual Caster (the wizard one), i.e., Gentle Repose, although it meets all the necessary criteria. 
Would you mind including it there? If the omitting was deliberate, why so? 

Gentle repose is selectable. The first 2 slots are only for level 1 spells, gentle repose is level 2 and has to be added to book from a scroll (or another book) by buying magic ink.

Thanks for your reply :)
It's weird then that one can pick Skywrite from the dropdown, which is also 2nd level, with no ink available

Quote from linaoranssi >>

Thanks for your reply :)
It's weird then that one can pick Skywrite from the dropdown, which is also 2nd level, with no ink available

 ? You can't. Skywrite is also a level 2 spell and can't be added to the book except by copying it from a scroll or spellbook using special ink.

In the feat, the first 2 dropdowns are for the 2 level 1 spells you get for free. The 3rd+ dropdown is for any level spell you add later via the special ink. Skywrite and gentle repose are both available in the 3rd drop down.

Quote from DxJxC >>

Gentle repose is selectable. The first 2 slots are only for level 1 spells, gentle repose is level 2 and has to be added to book from a scroll (or another book) by buying magic ink.

 It’s not specifically “Magic ink” just a really expensive and time consuming process that also requires ink. Lots of ink. And lots of scratch paper and other stuff.