DARTH finally lives up to his name and joins the Dark Side
You will have a better idea after some lessons. I was 80kg when I started. Had a 12m and 8m on a twin tip.
Considering you will want to learn on a twin tip, it is good having a big kite for 15-20 knots. 11m or 12m. I loved my 12m in that range when I started. However over 20 knots you need something smaller, say 8m or 9m.
If you want one kite maybe 10m. Try get two - 12/9m or 11/8m.
All big brands have "allrounders" which is the style of kite you will want. Get two of the same kite and one bar/lines.