A single soccer field will do, although you can't get too much speed going. With my 5m kites, I've found that after about 2 or 3 dips, I have to turn
around.
Obviously, watch out for those soccer goal posts, always make sure you are down wind of them (imagine getting lofted into one, UGH!). Somehow, my
kites are stragely attracted to football goal posts too.
Any riding is good riding. If you can crank in a small field, you'll be that much better when you get to a larger field, or frozen lake when winter
comes around.