If I understand you correctly, you have a main account and a second account currently, and the second one may not be active right now.

You can invite yourself to start a trial account from your main account or the second account (if you reactivate it) and create the trial account. you can group a lowbie from the trial account with a lowbie from the linked account and they will get the bonus. While you are on the 10-day trial you will be limited, such as max level of 20, no trading, no using the AH, no TBC, a host of limitations.

To lift the limitations of the trial account you must activate the account to a normal account. you can do this online or get a box from retail.

Since you give the referring account a free month and you get a free month with a new account on top of the 10 days, the initial cost of a new account is offset a good bit. A battlechest of WoW and TBC is 29.99 at gamestop right now, and the RAF generates 70 free days of account activity, which is roughly $35 of value.

You can get things in motion right now, for example you can log on to your account from work or school and invite yourself, then go to your email and follow the links and set up the account before going home. You could stop and buy a battlechest on the way and turn the trial into upgraded accounts when you got home.

Regarding when you can gift levels, you could group your new account guy and a lowbie from your main account, get them both to level 3, and the guy from the new account could gift a level to a level 1 or 2 on your main account. not smart to do since leveling is so easy that low, but possible. I believe the rare mount only becomes available once the referred (new) account pays for monthly subscription or something similar. Like I said, do some searching here and on the official site, the RAF FAQ on blizzard's site is pretty good.