Optimal Gaming Rig SSD GB

I'm currently in the process of customizing a rig through iBuyPower. I've heard plenty of consumers rave over SSD's. I've only had experience with HDD's, and that laptop ended pretty sour. I figured an SSD would be a good upgrade since it costs virtually no more than the 750GB HDD I originally intended to purchase. However, the SSD I looked at was only 60GB. That sounds like significantly less storage space. Is it that SSD's require less storage for these games, or is it as bad as it sounds? Two more quick question: Do I need a data hard drive/SSD? What does it do? I'm going to assume it handles file storage and anything that doesn't belong on the gaming SSD, but correct me if I'm wrong. And do SSD's have less likeliness of crashing?