There some folks struggle with this, it is a learning curve. Even if you are new and had all the resources available to you. A reefer has to know what to do and what to watch out for.
My tanks are pretty much insta- cycled. What you need to do that is the following:
1.Live rock/sand from an current healthy system. While live rock and or sand from a places like TBS etc. are great, they need to be processed first to get rid of die off during shipping. If you are not going to put fish in right away, it is a great way to get started. Corals can process the ammonia and the ammonia from the die off will help with expanding the nitrifying bacteria colonies. But if you are not doing that, you need to add current system live rock/sand, and then only add a ammonia load your current system can handle.
note: you can also use seasoned media plates from an existing system.
note-2 If your are gathering live rock/sand from an existing system that is going to continue in operation. Be aware you are taking away that systems biome. Nitrifying bacteria grows and shrinks with bio-load. So be aware of how much you take out.
2. NSW, unfiltered straight out of the ocean. While many ppl argue that NSW does not contain anything that a mix does not, I disagree. It contains the seeds of a successful biome.
This option is not available to a majority of reefers, but a bucket of water from a heathy tank might help.
3. Knowledge from experience.
4. Start small and don’t over stress your bio load...
Truthfully the most difficult part for me when starting a new tank is not the cycle, but trying to keep nutrients in the tank. Corals that came from a healthy nutrient system are now in a system that wants to rapidly deplete itself. it is all about testing and having the proper additives until the new tank becomes stable.
If you check out my sneeky pete build you can get an idea of what I did...