Based on an article or post I read not long ago most of the 'bottled bacteria' products don't work that well. There was one, called Bio Spira, no longer made under that name, that did work, and it's under a new brand name but I can't remember what the new name is, sorry.
The choice to cycle using fish, or using only pure ammonia, is yours to make. Personally, I prefer not to use fish, because if you make a mistake or don't do enough water changes, the fish are the ones to suffer the exposure to ammonia. If you use only ammonia, no livestock will suffer if a mistake is made.
It can take awhile for a cycle to be complete. Once it is complete, you must add fish slowly, as the bacteria, [BB, for beneficial bacteria], take time to increase their numbers to handle the extra load of ammonia produced by adding more fish. Adding all the fish at once usually overwhelms the filter's BB and the fish get ammonia poisoning. Patience is the very best friend you have when starting a new tank.
If, however, you know someone who has a tank running, or can get some media from a local store perhaps, it's possible to jump start a cycle. You either add some well used media from a well established filter to the new filter, or pour the cleaning water from a well established filter into a new one. The cleaning water.. [ I call it squeezings, or rinsings ], would be very dirty looking, containing all the matter the filter had removed from its tank, but that will also contain a large number of BB, who will colonize the new filter.
If you can get squeezings, or rinsings, or used media, you can add a couple of small fish right away. You still test, of course, to be sure all the levels are as they should be.. Ammonia 0, Nitrite 0 and Nitrate <20 ppm.. but it should be fine done this way. I start every new tank by 'seeding' the new filter with squeezings. For sponge filters, you can soak the sponge in squeezings and give it a few good squeezes before you put it in the tank. May take a bit longer in the case of a sponge filter.