The old adage, "You get what you pay for.", does apply with kites to some extent. The least expensive sport kites you can get your hands on are best left on the store shelf. Even though it is hard to spend a good chunk of money on what most people consider a toy, trust me, it is worth it to make the jump past the toys and get a worthwhile kite. Cheap kites tend to be small and made from heavier material and rods than more expensive kites. They require a greater wind speed to fly and will fly faster, be twitchier and harder to control. They may not be as durable as kites costing a little a little more. They may not have a supported sail that will hold it's shape out of the wind, either being flat or with a floppy sail not supported by "standoffs" or "whiskers". A sail with standoffs is required for the more advanced moves, tricks and unassisted ground launches.
You're probably thinking, "that's fine, but how much are we talking here". The good news is, not that much. It only takes $40 to $45 to get a kite called "The Beetle", which has a wingspan of about 4 feet. Is it the equal to a $150 to $300 kite? No, but it's a good start. It has a big brother called "The Alpha +" at about $80 to $90 and has wingspan of about 7 feet. It is a big step up in flying ability and is well worth the extra cost if you can swing it. These are just some examples. There are lots of good reasonably priced kites out there. Talk to your local kite shop or one of the many on the web about others. I'm just hoping to convince you to use that $30 on something useful, rather than flushing it on a cheap kite that will be frustrating instead of fun.
The next piece of gear that can be a little hard to get past is flying line. Just any old string doesn't cut it. At least not very well. Think of the lines that attach your hands to the kite as been much like the suspension on a car. If the shocks and springs are soft and sloppy, your car is unstable as you drive. The same thing happens with your kite with stretchy lines. You try to turn the kite, the line stretches and nothing happens for a while. Good line can turn a kite from being a handful, into a kite that's a blast to fly. The material that the line is made of is called Spectra and it will cost about $20 to $40 depending on the strength and length.
You may notice that some people have literally, bags full of kites for every wind condition. If you can only have one kite (been there), buying a range of lines will get you a lot of the same effect as having Super Ultra Light, Standard and Vented kites, for lots less money. The weight or strength of flying lines varies from as low as 35 lb. to as much as 500 lb. or more. The weight of the line has a significant effect on the light of the kite. Using a light weight, such 50 lb., with a low wind, 4 to 6 mph can make a kite fly well when it would barely fly with 150 lb. It has a lot more impact than you would probably think. On the other end of the wind range, 50 lb. line would snap in an instant with 15+ mph wind. The heavy line will also slow the kite down and give you better control in higher winds because it is thicker, creating more drag as the line moves through the air. This is why 500 lb line might be used, even though you do not need that much strength.
One more aspect of flying line is the length. Most line on the kite store shelf tends to be around 50 to 75 feet in length. This length of line is just fine for a lot of fun flying, but for flying in competition, longer lines of 100 to 125 feet is worth it's weight in gold. The longer line gives you a MUCH bigger window to fly your kite in, which does 2 things for you. First, it gives you a much bigger palette work with in the sky and the other thing is that you have a lot more time to react to avoid crashes. This extra time becomes critical in higher wind and makes you seem much more in control, even if you're not :-) . Conversely, if you have a very light wind, in addition to using the lighter weight line, shorter line can pick up the apparent pace of a slow moving kite.
So much information, ACK!!!! Don't let it worry you. You may not have things set up perfectly and Mother Nature will really make it tough for you sometimes. Don't sweat the small stuff, make your best guess and don't forget to ask questions if you have any. It's a learning process that will take time to really get it nailed. I'm still working on it :-) !
Equipment That Doesn't Fly (at least you hope):
Don't forget that you may be at the event basically all day or maybe 2 days in some cases, so you need to be comfortable while your out there. First, don't forget the sunscreen and some good sunglasses because looking up in the sky all day is tough on the ol' skin and eyeballs. A tent or sun/wind shelter, chairs, water, snacks, appropriate clothing or anything else that makes things more enjoyable for you and/or family is worth bringing with you.