Yeah this game probably has one of the worst gacha systems ever...
I've done four 10 rolls and haven't gotten an SSR yet, and two of those 10 rolls gave all R items except for the guaranteed SR which both times was a weapon.
They also didn't add enough content at the start for earning Jewels... I've literally run out of sources to get them besides the 50 each day from logging in and the occasional login bonus.