I haven't gotten a three star despite playing daily for 3 Months now. In the same time, I got 3 5SSRs and 7 4SRs in FGO. Game also crashes frequently even when running it on a SD865 with 8GB RAM. Faaily rewards for gems is low and you will need to rely on campaigns and boss raid for gems. Even if you roll 100 times, it is very unlikely that you get a 3star due to the drop rates. Guaranteed drop is at 200 rolls or 24000 gems. You'll need to save around 6 months for a guaranteed drop.