Reef Crystals should have sufficient levels of Ca, Mg and Alk to promote coraline growth. That's all I use in my Nano tank, and there's coraline growing all over. I think the secret is live rock that already has some coraline growth. If you can get your hands on even a 5-10 lb rock like this, it should help. I've never tried taking coraline scrapings from someone else's tank, but I've heard it suggested many times, and it certainly seems like something that could work.
As for the test kits, I'd still get them. The magnesium kit probably isn't very important if you're not planning on keeping stony corals, though. Although I have learned recently that coraline actually uses more magnesium than coral skeletons.