[Q] Once I get crash reproducible what next?

Ans: This is very wide question and really depends on person to person. 3 things i know you can do is.

1. Report responsibly to the vendor Miscrosoft(IE), Google(Chrome), mozilla(Firefox), Apple(Safari)
2. Do complete Crash analysis and create exploit for fun and learning then responsible report it
3. There are some of the vendors who do buy browser vulnerability (legal)