Well, you sure could try, but the certification is not going to make you a 'good' or 'bad' trainer, it's your experience and your clients success... One of the trainers at the club I work at is just ACE certified, and their clients see great success... and about 2 months ago, a trainer left and she had AFAA, NASM, and like a degree in Phy. Ed.... clients didn't see any results...
So it's just on what you do, if you don't have the background and you know the basic exercises but don't understand the human body, get ACE, and get experience... But if you know more about the human body, like ATP, syntergistic dominance, etc... then you could go more NASM/CSCS/etc...