1. Create your own index/crawl and true search engine on top of it, rather than delegating that back to bing or Google. In doing so, solve or address all the related problems like SEO/spam, and cover the “long tail” (expensive part)
2. Monetize it somehow to afford all of the personnel/hardware/software costs. Probably with your own version of Google’s ad products.
3. Solve user acquisition. Note that Google’s user acquisition process involves multiB/yr contracts with Apple and huge deals with other vendors who control the “top of funnel” like Mozilla Firefox, and that this is the sole purpose of chrome/android/chromebook/etc who you’ll never be able to make a deal with. You will probably at the very minimum need to implement your own platform (device, OS, browser alone probably won’t cut it).
4. Solve the bootstrap problem of getting enough users for people to care about letting you index their site, without initially being able to index a lot of sites, because you are not important enough.
5. Somehow pull all of this off in plain site of Google (this would take many years to build both technically and in terms of users) without them being able to properly fend you off
6. Somehow pull all of this off in spite of the web/web search seeming like it’s going to die off or fade into irrelevance
OR you can dedicate a decade of your life to something more likely to succeed.