Wasting a Miracle ticket opportunity is a decision you may regret later. They're the #1 item worth spending on. Everything else provides far less value. With Belial, Amaterasu, and Svarog your team will be nigh unstoppable. With only Belial your Fire team will be pretty lackluster.
Also, there's people who've gambled hundreds or even thousands of dollars trying to land what you've happily stumbled upon.
The event schedule is not an important concern, especially if you have a primary eidolon already. 1-2 SSR weapons do not make or break a build. The difference in damage from SR Disaster weapons is only about 3% per weapon (assuming both Assault).