Success or failure depends on tank size, how well the filter is working, how often you are doing partial water changes, and how much food is going into the tank.
If the tank had no fish left, I might have just left the water as is. That way the bacteria that you want to colonise the filter have plenty of waste to eat and multiply. By removing most of the water, you may have removed most of the ammonia, so there is now less driving force for the filter to become colonised with bacteria that can break down these toxic chemicals to nitrites and nitrates. Also, if you leave the water as is, the reduction in ammonia and subsequent increase, peak and decline in nitrite will be more obvious. If you record all these things, then you can see when it's right to start adding fish again. Remember, ammonia and nitrites are the most toxic. Nitrates are less of a problem, and can only be removed by water change. Nitrates are also plant food, so they will support any real plants you have in the tank, but it also means algae may grow. Patience and time is your friend here, although I appreciate that you feel you've already waited a long time, since May.
One thing you could try when the ammonia is back to zero, is to add a small amount of fish food every day. If the filter has been colonised with bacteria, then ammonia should not get too high. It will take a little while for the fish food you add to break down, so you need to give time for the ammonia to increase.
Try reading this:
Can I Use Fish Food to Cycle My Tank? (and How It Works)
I started with Zebra Danios. They're quite hardy, and none of mine died from tank pollution. The only one that died had some kind of weird genetic mutation. It grew far bigger than all the others, and eventually became sick. Make sure you buy fish from a reputable shop. They're more likely to be healthy, and less likely to be carrying parasites. Once you have added some fish, you can change a proportion of the water regularly. Changing 1/4 of the water once or twice a week should help keep your new fish happy. Once it's settled down a bit you can partially change the water less frequently, but keep an eye on nitrates, and test for ammonia and nitrites if you add more fish.
Another thing to bear in mind is that your fish breathe the same air that you do, because it's pumped into the water via the bubbler. If you redecorate, then some of those paint fumes end up dissolved in the aquarium water.
It might help if you tell me your tank stats. How large is your tank? What filter? Do you have gravel?
Post a picture if you like.