A cheap used Hobie 18 or similar is a good place to start the cat learning curve. They are pretty tough, heavy but durable when it comes to surviving all the mistakes a newbie sailor is going to make. Much better to learn on something you didn't pay too much for, then sell it, get a lighter, faster, spinnaker cat once you are further up the curve.

I once saw two new guys (new to cats) take a new (to them) Inter 20 out in 20+ knots for their first sail on a cat. There were about 10 of us Inter 20 racers at the regatta standing on the shore. We were not going out, the race committee had already cancelled racing for the day (too much wind) we advised these two it was not a good time to "learn" but they were determined to give it a go, they were after all, very experienced mono sailors...

They made it about 100 yards off shore when the first gust flipped them and they spent the next 45 minutes driving the mast tip into the muddy bottom while trying to right it, with no idea of how to right it.

So, if you are going to learn, get Rick White's book, then pick a boat that's easy to learn on. Easy being less sail area and strong hulls/mast which will stand up to a lot of abuse. Any old Prindle, Hobie, or Nacra is a good place to start. Most F16's are not so forgiving of any newbie mistakes and any new boat is going to be expensive to repair.