Ok, well, you have a tough fight ahead of you to keep your fish alive then. Next time fishless cycling will save you this headache. This is what you need to do:
Test daily for ammonia and nitrite. Nitrite probably reads zero right now, but you need to know as soon as it starts rising.
Do not add any new fish until both tests consistently indicate zero.
Change water as needed (based on test results) to ensure that ammonia doesn't exceed 1 ppm and nitrite does not exceed 0.5 ppm prior to the next water change. Gravel vacuuming can help, but won't make a huge difference at this stage.
Expect to see a reduction in ammonia beginning one to four weeks after the tank was first stocked with fish. At the same time nitrite, which is even more toxic, will begin to appear. Roughly a week after the first appearance of nitrite, you'll see it drop to zero and then you're good to go.
Estimated times may vary and are a function of water temperature (higher is better within the tolerance of the fish), concentration of ammonia in the water (higher goes faster, but tends to kill your fish), characteristics of your filter including flowrate and oxygen content of the water, and random effects such as the number of nitrifying bacteria initially present.
