Outside of the extreme basis of my post.
You'll need an AS number, IP ranges (v4/6) from a RIR (v4 may be more tricky these days).
Either DC space, or servers with a BGP feed, a session and a provider allowing you to advertise the above ranges.
BGP speaking software such as bird.
There's a whole lot more to think about but that would at least get IPs advertised and traffic moving.
Simply though, you will need at least some knowledge of BGP....