Live rock/Live Sand

[MilanoMami24]

I'm starting a 75 gallon FOWLR. I have heard you can use some live rock and some base rock and eventually the base rock will become live rock. I heard the same thing with the sand. I plan on using 40 lbs of araganite (carib sea) and 40 lbs of Arag-Alive (also by Carib Sea). But my question is how much live rock to base rock would i need? Could i do 30 lbs of Live rock and 50+ lbs of base rock?? Or should I do half and half, im trying to find the most cost-effective option, im still in high school so money is kind of tight lol.

[leebca]

Live rock cannot be made from base rock in a home aquarium. More information on this can be found in this post, including a recommendation for how much live rock to use:
What is Live Rock, Anyway?

Much depends upon the kind of system you will be setting up. Using base rock is fine, but the use of that depends upon what you expect to get out of the rock. If you want or need denitrification from the rock, you need to buy live rock to 2 pounds per gallon. If you're just interested in the rock performing nitrification, you can mix the rock as you like. See: Denitrification v. Nitrification

You posted this in the Saltwater (Fish-Only) Aquariums Forum, so I'm assuming the goal is a fish only with live rock (FOWLR) aquarium. You might want to read this to give you some ideas and things you'll need:
Setting Up a FOWLR Aquarium

I wouldn't bother using live sand. If interested in saving money, buy 'non-living' substrate. Nitrification bacteria are everywhere. They are in the air, water and soil. Why buy them? Use regular sand and give it time to host the bacteria that are needed. You'll find that going slowly is your best chance for success in this hobby. The use of live sand really doesn't speed the tank toward maturity. (See: The Mature Aquarium). It takes time.