It takes years before you become any good at writing. Or any good at anything for that matter.
And you need to know your readers.
And take concrete examples that readers can check and generalise. Quite simple. actually.
The source of all great mathematics is the special case, the concrete example. It is frequent in mathematics that every instance of a concept of seemingly great generality is in essence the same as a small and concrete special case.
While not devoted to original research, the website About is a fantastic resource for stochastic calculus. This website makes for a nice reference alternative to Shreve & Karatzas or Revuz & Yor. Another website that is devoted to original research is Rough Volatility, and indeed the community is relatively active with the most recent post (as of the time of writing this post) as of June 22.