Scooby, with an API kit and that bottle of Prime, you are off to a great start to your planning, actually far beyond what must happen to thousands of people who walk out of pet shops about to go and possibly kill their first tank of fish, lol!
CaribSea is a distributor of crushed coral and various products that get used in the salt side of the hobby (and fresh) which leads me to wonder whether the product you are looking at might be one that raises mineral content tand pH. I totally don't know, so hopefully some other member might or indeed the shop owner might. It's just a caution as you of course don't want a substrate that's acting as a major chemical on your water without you knowing it! Again, most likely it's just fine.. it's just a question on my part.
To me, plants and fish are the icing on the cake. They are the big reward that comes to the beginner weeks or months down the road after the "blood, sweat and tears" of learning the core skill of how to deal with biofilters and understand them hands-on! Putting plants and fish in a tank less than a month or two old is, to me, kind of "non-hobby" almost because it kind of moves the mental attention in on the reward and takes it away from a focus on learning the core skills that will be useful for a lifetime in the hobby. I mean, you can learn them later but I just have this feeling that "right off" is the best time.
I don't of course mean that I don't love plants and fish, in fact they are ultimately the huge focus. But it's a focus that lasts for years (many plants and fish will live comfortably and healthily in your tanks for years on end) and stays the same day after day, month after month. The first 4 to 6 weeks or so are totally different.. often the only real chance you get to really focus in on the arcane story of the chemolithoautotrophic little fellows that are so much your invisible magic friend through all these coming years! That is why I so much like seeing beginners take on the fishless cycle learning!
Gosh, I'm really on about it today, sigh!
~~waterdrop~~