首先的英语高级表达有

1.in the first place 
2.first
Relative explainations:
3.begin...with 
4.for one thing...(for another) 
5.first of all 
6.to begin with 
7.imprimis 
8.in the first instance 
9.firstly 
10.of all things 
11.above all 
12.to start with 
13.primarily 
14.threshold 
15.at a first brush 
16.first and foremost 
17.the first thing 
18.in the beginning 
Examples:
那不是个好办法,首先没人会帮我们的忙.
It is not a good idea.For one thing,nobody will help us.
我首先是一个教师,其次才是一个作家.
I am a teacher in the first place and a writer in the next place.
婚姻首先是一种契约,它必须以公正为制约.
Marriage is,first of all,a contract which must be governed by justice.