As you may know from my previous thread, I have recently lost my job because I was overqualified (worked for 4-5 months after I graduated this year) and the manager decided to let me go. Manager also let some other people go because of limited budget and they don't need that many employees.
I have left the company yesterday and didn't ask my manager for a reference.

I don't know why. But, every time I see the manager, I didn't feel like asking or couldn't speak or couldn't think because they decided to let me go because I was overqualified. Every time I see my manager I feel so depressed and I have kept our conversation short. It wasn't like this before she told me...but I guess I loss a bit of motivation and the manager also knows that I am not feeling happy in a way. I was still doing work but it's not the usual myself with that 'big smile' on my face.
I will be applying for jobs next month.
Questions:
1) If a new employer asks for references, is it O.K. for me to tell the new employer that I need some time to contact my references?
2) Does the new employer expect me to have my references ready in place?
3) Should I contact my previous manager ASAP and let them know i will be using them as a reference? (I believe she is not working in the next couple of weeks until early January)
Thanks