That's totally up to you! You can reinfuse the same oil!
Fill that thing up with busted up bud, decarb it and then cover it up with oil and infuse.
Strain and press out the oil in a French Press and use.
If it's not strong enough for you, the decarb some more bud and use the same oil!
Walmart usually carries a 19 ounce bottle MCT oil. That's a good size to start off with. Get a couple of bottles