The Lonious Monk
Celestial Souljah
We really don't know that he could have made more resources. We know what the time stone does. The reality stone alters one's perception of reality. The mind stone is mind control. Power, soul, and space stones still vague in what they do, I don't think Thanos has the ability to create things out of nothing.
Besides that, he had already theorized genocide to be the best solution while everyone else's solutions failed and his entire race died. He's basically Superman's father on Krypton, but survives and says "my people didn't listen to me, now the entire universe will."
This. A lot of the people that are criticizing things from the movie don't seem to be grasping everything the movie shows. At no point did Thanos create something out of nothing. The reality stone might have been his best bet because alone it only alters one's perception of reality, but enhanced by the other gems maybe he could have done some bonafide reality warping. The problem is that Thanos didn't really have time to mull that over after he got the gauntlet.
And both I and now @Soul_Rattler have pointed out, Thanos didn't just come up with his philosophy from nowhere. He had literally been putting it to the test over the course of a long time and saw success where he intervened and failure where he didn't. It wasn't about just committing murder. If that was the case, he would have just killed everyone he fought, but recognize that after every battle, once he got what he wanted, he let everyone live. He had no interest in wanton killing. He was culling the herd to save the universe.