Immortal monster: I'm planning to go with a Solar from D&D. But definitely something that looks or can look like a human most of the time.

Magic system: probably the most difficult choice, the ships I imagine can do more short term good, but magic has near limitless possibilities. I'm not sure which power system I'd use, maybe mage the ascension.

Civ: I'm hoping I can do some tourism between turns and just explore, and maybe, as a Solar, help my armies win should war be necessary.

Post Scarcity: The best choice if you care about improving the lives of others. Most disease in the world is either caused by deprivation or adverse working conditions (everything from stress & overwork to physical hazards). I can eliminate the majority of human suffering overnight with this choice. Without limits on the number of microcentrifuges, or needing to work for loreal if they wanna be paid, every vaguely interested researcher will be free to work on curing chronic illness.

With an abundance of resources art and literature will fly into a new golden age, every burger flipper and accountant now free to do something meaningful with their lives.

My plan is to just enjoy life for the most part, learn magic, go on adventures and help those in need. I can literally see morality as a Solar and can teleport and speak all languages, I'll help solve conflicts and make friends around the world while the planet transitions into a utopia. Using my powers to lopp the heads off any would be tyrants who might try and assert themselves.