Fetching details from the dictionary...

first (of all); firstly; to begin with; before anything else
probably; most likely; almost certainly; virtually
more or less (satisfactory); on the whole; reasonably
anyway; at any rate; for now (at least); for the time being
先ず自己紹介をしましょう。
Let's start with self-introductions.
先ず最初に計画を立てた。
First of all, I made a plan.
先ずは落ち着いてください。
First, please calm down.