I would be nervous about using a knock-off strap. If it fails, your camera and lens fall to the ground. Apparently this has happened with Black Rapids, but they have a brand to protect; the knockoff has no brand to protect. I would be more nervous of a product when they have nothing to lose.
Note that a Joby and a tripod are radically different and not at all comparable because you use the Joby to wrap around a pole whereas you use a tripod to create a platform onto itself. I do not want to dissuade you from the Joby, but I don't want you to misunderstand that it is fundamentally different than a typical tripod.
Re: ball heads, yes, you can use other ball heads with a Gorillapod. I have two heads: a Really Right Stuff BH-55 and a Markins 3QT. The Markins is $310 USD and the RRS is $575 USD. Neither is inexpensive. Both are awesome. My advice is to save up and get a great head. When you are new to photography, it's hard to fathom why you would want to purchase such an expensive head until you have used a lower quality head. There is a real difference between a good one and a bad one. With a good one, you mount a 70-200 f/2.8 II and it does not droop; with a bad one, you mount the same and it droops. You spend an inordinate amount of time trying to figure out the extent of droop that is sure to come. Do you want this? Get a good head and you simply worry about how to get a good shot rather than the failures of your equipment. I struggled with this when I started and then I just bit the bullet. Like a good lens, I do NOT regret buying a good head (or a good tripod). I will skimp on a body, but I will not skimp on a lens, tripod, or head.
That said, I cannot comment on the Manfrotto heads because I have not used them. There are a lot of threads on CR re: getting a good cost effective tripod and/or head. Check them out.
One last thought: there are a lot of up-front costs that you are facing here. My advice is to get the camera, lens, filter, card, and strap. You can shoot with this. Once you learn the camera, save a little more and get a good tripod, head, and other items that you need. Take it one step at a time.
