As Shadygrove mentioned, you can retrieve material now. That said, you should also get a fair amount from the gear you SB 100% and break down. Towards the next tier of iLv, there is an increased chance that you'll actually get the next tier up when you convert. Bear in mind that you can get unlucky and still get the lower tier materia as well.
There is also the option of negating the cost of materia by placing other items you have up for sale, or farming them. You are essentially 'farming' the materia you need this way instead of relying for RNG to be in your favor. If you're on a budget, or at the mercy of the MB due to limited resources, sometimes you just have to wait things out a bit, and/or grind.