My personal thoughts :

1) Rather than save up to do 10 pulls, I usually do one pull for free per day, then one ruby pull. Doing a single 300 ruby pull per day costs 250 rubies, as you get 50 rubies back from the quest for spending 300 rubies. So, 11 pulls once per day is 2800 rubies, vs 11 pulls for 3000 rubies (save 200 rubies). Always do the blessing thing, as it's only a tiny boost in chance, but every bit helps.

2) SSRs will come, but there's a few important girls to get :

a) Lu Wu (needed for Asgaard)
b) Ren Qing-chen (If dated to gold 100 her defense is 10K and up, best defensive stat in game)
c) Mateo Maya (Instant win in Infinite Tower, only obtainable via Asgaard Conquest)

Beyond that, the SSRs you get from the ruby are decent enough, Mako is probably the hardest hitter.

Don't forget to boost Oda Sayoka, she's only an R, but she's the only free healer in the game, so you'll be using her forever.