Could I have a 19 meter as a first kite?

No

How's that. I wouldn't do it. There's a couple of reasons. No matter when you go out, you require a given amount of power to get going and stay up wind. A bigger kite allows you to get that amount of power out of low wind.

Low wind is the most difficult circumstance under which to kite, except for extremely gusty winds. Most kites will fly in a given minimum amount of wind, around 6 to 8 knots. They will all water re-launch at a slightly higher amount of wind, plus or minus.

When you start with a big kite, you are starting at the edge of the window in being able to fly a kite, being able to launch a kite, being able to get going or stay up wind. It would be very frustrating for you. Also, when you only have one kite, you tend to fly it when the wind is anywhere near what you need. So, you'll drive yourself crazy in 6 - 8 knots, and crash the kite (and wear the kite out), and on the other extreme, you may kill yourself. If you are truly in a light wind area, start with a 12 - 15 flat kite (max) or a 15 - 16 C kite.

If you live in a normal area where winds are too low or around 15 -20, start with a 12. You'll be glad you did.

START WITH A USED KITE. You'll ruin your first one soon.