I was asked by someone who is thinking to go to grad school in Econ. that which book is better for 1st year econometrics class.
The following is my answer;

I think "Hayashi" is better for preparing first year course work.
Especially, to read first 3 chapters helps you a lot.
But, if you will major in some applied microeconomics, you may end up
buying "Wooldridge" book too. (H- is good at Macro and time series, W-
covers microeconometrics very much.)

Usually, mathematical statistics is covered in first few months in
metrics class.
The following huge textbook covers math quite well. This book is
also quoted often, so it may worth buying as a reference book.
"Econometric Analysis"
by William H. Greene

If you would like to learn econometrics without technical issues, the
following text book (for undergrad) is highly recommended.
"Introduction to Econometrics"
by James H. Stock, Mark W. Watson