First, Beginning, Outset
Noun and の adjective
さいしょ
最初はとりあえず生で！
I'm gonna start with a draft beer!
コウイチの最初のかの女の名前はコウイチ子でした。
Koichi's first girlfriend's name was Koichiko.
お前本当に下手くそだな！初心者でもこんなに下手くそじゃねぇだろ。俺が最初にこのゲームをプレイした時は、お前よりずっと上手かったわ。
You’re awful at this! Even a newbie couldn’t be that bad! When I played this game for the first time I was way better than you.
The most first thing is the first thing.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.