I don't want to be rude, I just don't want to see you get dissapointed or have a fish die later on. If you truly care about your fish, you'll read what everyone has to say, and take it to heart. If you don't care what other, experienced people have to say, then stop reading now. Get your fish, and let them die.
I agree that you have made a poor choice in fish tankmates. While it is true that your gobies can live in fresh water, living is not the same as living well, or thriving. The same goes for a figure eight if you decide to get one. Mine would never touch anything more than a ghost shrimp, but that doesn't mean others wont - ask other members about their puffers! There is a strong possibility that they will turn agressive toward other fish. An F8 puffer is also brackish, and will not survive long in fresh water. They can only tolerate the fresh water conditions because they were blessed with evolving in an environment where the water fluctuates regularly. Again.. they are brackish, as are bumblebee gobies, and shoule be kept as such. Bumblebee gobies can also be rather territorial. While they may be small and adorable, they are feisty, and I wouldn't suggest putting more than what you already have in there.
If you have done research enough to see that your neon's needs are too narrow, then you also should have realized that they need 6 or more for a school, as well as the puffers and bumblebees need brackish water. Rams are even more sensitive to water fluctuations than the neons, so good luck.
Volume Calculator You are at 88.66 liters, or about 22.79 US gallons. I understand this isn't exact because of rocks, ornaments, etc, but in the real world, that isn't how your tank is calculated.