I mainly use size 9mm x 8mm double cap rivets in my bag making because I find the post is long enough to get through quite a lot of layers, 9mm is the length of the post and the 8mm is the width of the cap, I also like them because double cap rivets look great on both sides.
I've had a rivet press for a long time but I can honestly say it's only recently that I've really got to grips with it. I was crushing a lot of rivets but I've worked out that if I push the rivet part without the post into the die and the part with the post through the fabric and press together I have a much higher success rate
I got my press from this shop on ebay, I also bought my dies from them too, that way I was sure the dies and press work together
If you don't have a press then you can always use these rivet setting tools, again bought from ebay, they work just as well, they just require a bit more elbow grease