Wow! So I wasn't expecting these questions. I do not take vaccinations/medicines before traveling. But I definitely bring vitamins.
Not sure about health insurance.
Travel insurance, I prefer in case your trip has to be cancelled due to weather, shortened due to injury/medical emergency, etc. It protects the rest of your trip for a fraction of the cost.
I defff try to eat healthy while I travel, but do not limit myself to vegan or gluten-free.