I guess it depends on why you want Saki. I have Hina if I want a ninja and Shao if I want ranged assassinate. I don't like relying on assassinate anyway so Saki is very low priority for me. Can also depend on if you have other black units (or units in general) you want to level up first. Also getting those 3 Ninja awakening Orbs will take time.

Getting Spica makes sense because you will see an immediate benefit with CR and maybe extra skill. Another option is simply awaken 3 more units if you have the resources. I went that way during the Memento event and I don't regret it - I'm up to 6 awakened units plus 1 ready when its leveled and I have more gold. A stronger core team (even if you are Awakening just to make your core team units better) has long term value. Of course anything with a decent passive ability should be priority though. But I'm a free player so I pretty much have to make do with what I have.