The FUT 15 Millionaire Trading Center has proved to be an incredible resource for making money in Ultimate Team. With the Trading Center, you have access to a revolutionary autobuyer/autobidder that automatically adjusts trading margins so it essnetially works on autopilot. You will also have access to secret trading lists and tips and you will also be a member of an exclusive community of pro FUT traders. It is the single easiest way to make money in FUT 15 so check it out! If you are interested, I've also written a full review.
Go to EA's Origin account creation page and sign up for an account there. Make sure you use an email that is not currently signed up to Origin, as it will not allow you to do so. I also noticed that the sign up page isn't the greatest and doesn't alert you of this so just make sure you're using a completely different email. From there, if you try to log into Ultimate Team, you'll see that you need to play FIFA 15 and link an Ultimate Team to this account with an Xbox Live account. However, you can't use your own, so you'll need an account.
You need to create an Xbox Live silver account -- that is, the free version. If we were creating Gold accounts all the time, it might get costly, and we only need the web app anyway. When you sign up for your account, make sure you do not enter any credit card or payment information but still create an account that can connect to Xbox live. Also make sure you sign up with the same email you signed up for your Origin account for!
Once it is created, play FIFA 15 with it and start an Ultimate Team. You may be prompted to match it to an Origin account and then you should match it to the one you created earlier.
From there, you can trade between the two accounts and effectively have two trade piles to utilize.