RAID isn't something you wanna do unless you need the redundancy, such as if you have massive amounts of data and no real backup strategy. To date, the only data lost in a RAID array was from when I had a software array go poof because I forgot it was done in windows and I erased the windows install... yay me?
But in all honesty, just grab a 250GB SSD and get it over with. You are going to have to reinstall the OS anyways if you try to raid the 64GB SSD with another SSD.