Wait for the $59 membership if you want to send in bulk submissions only.
I recommend having a look at this thread when it comes to declaring value of your cards Declaring PSA Value
There’s no right way to do it, it’s really up to you. Unless you’re talking cards worth several thousands of dollars, people usually send them in the bulk $100 per card.
That being said, you’re not covered for the full amount if a card gets damaged at PSA or your return shipment gets lost you will only get whatever the insured value you put in with your submission.