I think you already have your answer from Colin T. It will be whatever numbner it takes to keep your fish safe from ammonia and nitrites. A typical value would be maybe 30% daily but you might get by with a bit less if you took the time and effort to test your chemistry. The 2 weeks with nothing in the tank is a waste of time. You either need to do a fishless cycle which will start the day you have some ammonia and a test kit or do a fish-in cycle which will start the day you add your first fish. The fish-in cycle will take a bit longer because you will need to keep the levels down in your tank water to let the fish live. This means the bacteria won't grow quite as fast. In a fishless setup, you can leave higher ammonia levels in your tank and even high nitrite levels and not harm any fish so it takes a lot less water changes. There is a sticky at the top of this forum for fishless cycling and it is what most of us would suggest. There is a link in my signature for doing a fish-in cycle because lots of people don't or won't read the article on a fishless cycle. Those people need a rescue and that's why the link.