Guys i'm a newbie so pls excuse me if this question has been asked before a million times.

I just took my 2011 Maxima SV and now i'm about to buy an Eibach pro Kit from one of the member here.
i came across camber kit on eibach website.

Currently the car has the stock 18".
In future I'm thinking of doing a 19" or 20", I'll be changing rims in future so do I need to buy the camber in future if I go for a bigger rims or do I need to buy now as I'm lowering the car with Eibach

Can someone pls tell me what is the camber kit and why is it needed?
Any info would be appreciated

 

oops forgot to ask one more thing
Do I need to get spacers along with the eibach spring kit?

If I need to get spacers then what is the size that I need to get and what is the brand that I need to?