Karting equipment is what isn't always seen at the race track, but sometimes is. Whether it's how you haul your karts to the track, or the things back at the garage that help your weekly maintenance.
There are some things you will need, if you really wanted too you could get by without some of these, but it wouldn't be worth it.
When I started out, I put the kart in the back of a truck. This works well but we eventually graduated to an enclosed trailer, which is very nice to have.
Nobody wants to work on a kart on the ground. You would have to put a block underneath the kart to make changes. There are better ways. A simple kart stand is cheap and lasts a long time, and folds up pretty well too. There are rolling kart stands and others too for karting.
To find out total weight and to also help find places to add weight and make handling adjustments you need kart scales. These are not hard to find and range from bathroom scales from your local department store to racing scales with stands to make things level.
An air tank is needed at the race track to make air pressure adjustments. You can get a small one, as karting tires don't need that much air.
A kart tachometer is the key to keeping track of these things. Usually mounted on the steering wheel for viewing while racing, or the floorplan, these can show you the numbers for that data.
There are things that would be very nice to have but not everyone has the money, or is racing competitively enough to have a need:
A kart tachometer is probably needed, just so you can keep track of engine heat and rpm at least. The lap times are very handy as well. But there are ways to take that data from the kart to a computer to analyze all the important data. This can get pretty technical and a kart data logger can be of use.
Everybody would love to show up in a 30 foot trailer but even just having a smaller trailer is very convenient. Small kart operations consisting of one kart usually don't need a trailer but still would be useful. If you have many karts, your going to need more room.
There are various other types of karting equipment out there, and new ones invented all the time, try to keep up.