Hello there. If you’re looking for live sand, CaribSea Arag Alive is the most popular and good quality, And their “special grade” reef sand is the most popular.
Your old rocks should be good, and just needs some seeding. This is provided that they were never exposed to copper or anything. That said, they may have lots of organics on them. If so, you may want to give them an acid bath first.
as for seeding your tank with nitrifying bacteria, any brand of product will do well. Many of them claim to be the best, but all of them are sufficient. If I had to recommend one, I’d say Turbostart (purple bottle). It’s good quality.
As for electrical equipment such as a protein skimmer, lights, etc.… There are so many options to choose, I’d say it’s more a personal choice than anything. Fortunately you don’t have to make that decision for at least a few weeks. So you have plenty of time to research. Meanwhile you can prepare your rocks, and begin growing your bacteria.
*I am personally not a fan of any small protein skimmers. Even managing the fish store, I’ve yet to see any that I’d say work well.