You can do a pure ammonia fish-less cycle. I prefer this method as it allows you to control the ammonia and won't smell or make a mess like using raw fish/shrimp for cycling can.
If you use pure ammonia make sure its only ammonia, no other detergents/cleaners/perfumes, or dyes! Ace hardware janitor strength ammonia is a great safe product I use it to cycle my tanks.
I use the ammonia calculator at the bottom of this page (and the volume conversion calculator at the lower right) along with a needle-less syringe to get dosing accurate.
(the page has a good write up on cycling too).
While the tank cycles test ammonia and eventually nitrites daily and dose ammonia accordingly. Get you water change regime down now, it keeps nitrates from going through the roof by the time the cycle is done. 1-2x a week water changes should work (on a water change day test ammonia and dose after adding the new tank water in and letting filter run a bit before taking the test sample.
Tank is cycled when 24 hours after dosing ammonia (I usually dose for 2ppm) your ammonia and nitrite test shows 0 ppm (liquid test kit-strips are unreliable). Test nitrates and do water changes to bring them down low (10ppm or lower) and its ready to add puffers. Add all puffers at once, I strongly recommend drip acclimation, don't just float then dump out a bag. Also do not net and pull the puffers out of water, this stressed them which can cause them to puff, sometimes they cannot deflate and it can lead to death. One of mine jumped out of the cup used to transfer them from drip acclimation bucket to tank. I pulled her off the floor and put her in the tank quickly but she died the nest day.
I strongly advise against dwarf puffers with any shrimp (or snail) unless that invert is intended as food, case and point: