I am having trouble putting on free stuff from other people...I am not sure in which directories certain files have to go. I have been able to install everything from first party w/o any problems, granted everything has been free up to this point. The victoria, michael, and aiko models are free, and there is extra content such as poses, animals, clothes. Right now, they also have some sci-fi scenes and props for free as well. You might already have all that stuff though. Also, I am using the PC version of DAZ.
Additionally, I would recommend buying a platinum pass for a month if there is a bunch of stuff you want. I don't know if anything of that helps since I don't know what you bought or didn't. I wish I could help more. Keep us posted; it would be cool to talk to other people who are using the same product.