makatakam

If you only have one or two sets, maybe three, you will appreciate having the following in the order given, for the reason given.
1. 80'x90# for flying alone, practice, or flying with another flyer or two in limited space.
2. 120'x90# for flying with others at fests, or when you have the space, or in strong wind when you want to slow the kite down.
3. 30'x90# for really small flying areas.
Just remember, everything happens really fast on 30' lines -- don't use them near people or obstacles until you are beyond 110% confident of your ability to control the kite.
In the Midwest, this is a good way to begin. If it fits within your budget, get all of them at once. Remember that a 120' set can be cut down into shorter sets as they begin to wear out. This will happen sooner or later, depending on how often you use them. I do most of my flying on 80's. When flying with others 120's. I prefer 40' as my short set.
Your mileage WILL vary.