You can use feeder guppies not fancy. These are $1 a dozen at the most. You can cycle with two tuff fish like the danio too.
What kind of filter are you using? What kind of material (filter media) are you using to house the bacteria? The bacteria needs a good home. You can use lava rock,ceramic cylinders, an extra sponge or some synthetic medias such as bio chem stars by aquarium pharm co.. It will take a good 6-8 weeks for this cycle to complete itself. During this time you must resist the temptation of adding new fish, and you must add fish slowly. One here, then one there, not 10 at a time, your patience will pay off.
Get your self an ammonia test kit and a nitrite test kit keep tabs on these conditions and do water changes during the process. Dechlorinate your water and watch for drastic changes in water temp ( adding cold water), so you do not disrupt any bacteria forming .
The first bacteria to form (nitrosomas) will use ammonia for food and produce nitrite, the second bacteria to form (nitrobacter) will use nitrite for food and produce nitrate which is the least toxic and will be removed with water changes. Live Plants will aid with this too.
Once you have this bacteria living fish keeping is quite easy. The cycle is 90% and the least understood, the rest is pretty easy. I do maint. once a week about 1-2 hours every sat. morn with a 100 gallon, a 55 gallon, and a 20 gallon. ***NOTE: what ever you choose for a media for your bacteria to live * NEVER CLEAN IT*. Just a light rinse in some water removed from tank during a water change, and I rarely do that!