New site and 15 million pages, how to index?

Question

Google

A new site is launched, a new domain, and it has 15 million pages.
1. Is it worth it right away, from the first day, to feed the sitemap consoles for 15 million pages?
2. How is it correct to index my case without sanctions and within the framework of the crawl budget? Site from scratch, I remind you. No link mass, trust, etc.
3. What terms can be roughly expected? How much will it index (if it manages everything at all)? Week, month, year?

Answer 1

if budgets (server return) allow, Google eats 500k per day easily

Answer 2

1- yes, it's worth it
2- fill in the sitemap and increase the link, otherwise there is no way. Lightweight pages speed up the process.
3- I have a website with 30 million pages. 2 years, there are now 2 million in the index.
I speak from my own experience. You can write in a personal I will tell you the details from your project.
P.S. Without links, there won't be a big index.

Answer 3

Worth
it What is a crawl budget where did you get it from? If you are talking about Google, then it has a crawling budget of many billions of dollars, do you think to scare it with your microsite or something? Or are you worried that Google will run out of money when indexing?
If you boost, then manage in a month, if by gravity, then it can take a long time