Health coverage after losing my job: marketplace or Medicaid?

My employer coverage ended at the end of the month and I am trying to work out what to do as a data-entry clerk. I have been trying to stay organised about it. I think my income this year might qualify for a subsidy. How fast did coverage start?

Losing job-based coverage usually opens a special enrolment window, so check the deadline on the official marketplace site. I missed it by a day once and regretted it.