Wait to start those until your water tests say you need them. Cycling a tank is just the beginning of letting your tank mature. Cycling shows that your tank can process ammonia and nitrite, ammonia being the one that does the most damage to the life in our tanks. But you also need a bacterial foundation to be built in your tank for all of your inhabitants. I would start your skimmer and let it get broken in. Once your tank can process 2 ppm of ammonia in 24 hours, you can start adding a couple of fish and a small CUC. If your phosphates get above 0.1 ppm, I would run the gfo. Otherwise, I would leave that off as well as the uv reactor until your tank says it needs them.
As for water changes, try to change 5%-10% a week. If you want to skip water changes and just dose, people are successful with that, just don't dose something unless you test for it.