Hey, I was looking at some Ryze builds and the end game items had both MuraMana as well as Seraph's Embrace, both of these require that you charge a tear of the Goddess in order to get. So can you buy two of them as your first buy and they will both charge everytime you use a spell? Or would you have to do them one by one

No you can not. and your second tear will not charge at all because of the unique passive.
If you an item says unique passive they dont stack with the same passive name

so if you look at tear it says

UNIQUE Passive - Mana Charge: Grants +4 maximum Mana (max +750 Mana) for each spell cast and Mana expenditure (3 second cooldown).

we are looking at

UNIQUE Passive - Mana Charge:

any other item that says

Mana Charge will not stack with tear. since

UNIQUE Passive - Mana Charge: is also on manumune and arch angels staff that means they dont stack.

However, after you get a Seraph's Embrace or Muramana (in other words, fully stacked Archangel's or Manamune) you can buy another tear and start stacking it.

thanks sofa. left that out