Hey Helz,
Get a Trainer kite for sure. Kiteboarding is all about the kite and how the wind window works, learning the power zones and what to do when the wind gusts and lulls. I spent ages on a trainer when first starting. When the wind was blowing 8-10knts you can still get out and practice on your trainer.
Once you master the wind and the kite on a trainer you can get out on the water on a larger kite,
Lessons are a must! and you will need less of them if you combine them with a trainer kite. Never go out alone or if no one else is out on the water. Make sure you have an experienced buddy or someone to watch you.
Kite choice is purely up to you but my advice is to do your research and make sure you choose a kite that relaunches easy as you will be dropping it in the water alot. Check your local area and look at the brands ridden by most and check your local shop for brands that are well represented. This is so you can easily get spare parts or advice on flying the kite when you first start out.
If your in NSW check out www.nswkba.com.au for kite spots, local shops, kite buddies, social events.
All the best and I hope this helps? PM me if you have any other Q's