“先到先得”英文怎么说？

first come, first served.
这句话是接受某种服务时经常见到的

first come first serve

或者如果是像发送免费赠品但是赠品有限的话是
while supplies last

The early bird catches the worm.先到先得。

-----这句是英语谚语，绝对正确。

first come first served

He gets who comes first.这要看具体的语境的，我用了直译。