Rather than a hammock, spend the money on an Anubias (or other floating plant) to float in your tank. Provides hammocks, shade and hides. Money spent on plants is never wasted. Get more. Get a cave/hide (coffee cup etc).
You might get some Omega One or New Life Systems pellets (Betta size), a better quality food than Aqueon food. Good suggestion from Anubias: get frozen
bloodworms or mosquito larvae for treats. They like variety. Aqueon conditioner will do for now.
The API freshwater master test kit is available from Amazon for ~$20--to measure your ammonia, nitrite, nitrate and pH. Get some Prime and a thermometer and you'll get free shipping.
Your filter is a Tetra 3i. It's technically a sponge filter because it uses an air-pump to pump bubbles which circulate the water through the filter. Unfortunately, it's a really bad design; the water does not flow through the filter media/pad/cartridge, only over the top part. I wouldn't use it unless your fish actually enjoys it. For Betta purposes, a filter is more for cycling than anything else.
Eventually you'll want to cycle a larger tank or two for your fish to live permanently. In the mean time 2x weekly water changes will have to do. Ask about cycling when you have (a) larger tank(s).