Basically syncing to MS Exchange involves two different protocols. The full blown Exchange RPC protocol is what desktop clients use while mobile clients use the newer ActiveSync protocol.
The problem is that only iOS devices support ActiveSync, not Mail.app nor Address Book and Gmail does not support Exchange RPC protocol. So your only option is to use Google Sync for contacts, IMAP for e-mail and CalDav for iCal syncing.
EDIT: to sync multiple Gmails, first set up one Gmail as shown below, and then use some third party syncing application to sync the other Gmail account. E.g Soocial allows to sync 1 Gmail for free.
First open Address Book and go to
Preferences. There click the
Accounts button and select your (probably only) account there. Next, enable Google sync:
And enter your Gmail credentials:
After this your Address Book should start syncing to Gmail. It probably greets you with several collisions if you had contacts in both places, which you have to resolve manually.