How to maximize Citi trifecta/ecosystem?

I recently got my Citi Premier Strata Card, and I also have Custom Cash. What are the best ways/practices to maximize Citi's ecosystem? I have Chase trifecta but I am new to the Citi setup.

Also, I haven't had any luck with Citi's travel portal. It just doesn't load. Is it always this bad?

Here for the gains, thank you!