Bootstrapped, always. Most successful startups mostly start with bootstrap until they reach a point where they need more funds to do bigger stuff.
Eg: Meta(FB), Dell, Apple, Coca Cola, Cisco, eBay and so on.
Simply depends on the service / product being built.
Anything that requires hard sciences / real engineer needs funding to support talent and development. Other than that getting scrappy is a good place to start imo. đź‘Ť
Jorcus
Spark'n