When the battle starts, don't worry about boost. Get 2 boxes (use 
to get second if you only get 2 single boxes) and go to the bottom pipe if you get a trap item. Right after you land on the second floor set a trap and do this for both sides. This blocks the pipes from use on the base floor. Next, set a false box on the outside corner of the ramps, and remem where you put your traps.
In this map, green shells are better than red shells. Why? Because red shells can be out run, they crack when they hit the wall, and they can't get someone on the top floor.
When you get a green shell, let them know somehow and start circling in the main open space. They will come, because they are trying to pop your balloon. When they are going in circles with you (you may want to practice first), project the shell at them about half an inch in front of their path, which should get a solid hit. The point of blocking off the pipes and putting blocks by the ramps is understood here: enemies will try to use the ramps and attack from above, or try to flee and hit one of the boxes.
Bombs are ineffective in this map, except when the opponent is on the top floor. Throw it under them and it will still hit them.
Big bananas/bananas are good to block the pipes, but big bananas make a good fortress, because only a Bowser's shell or a bomb can get through. Find a corner and let 2 players duke it out by putting 2 big bananas behind you making no getting in or stealing balloons
Here's a good glitch: they hit you but you don't lose your balloon. It's called the pipe glitch: if they knock you into a pipe or you drive into it before your balloon pops, you wont lose it. Hide there when you have 1 balloon left and wait until you have a chance to strike. Beware though if they have a mushroom they can take that last balloon. Keep a mushroom with you and use it when they hit you and take there balloon. Don't worry about traps on top, since you won't get hurt.
Bowser shells are good if someone is going up the ramp. They can't turn and they can't destroy the shell. Follow them and when they go up hit them.
Use the walls. Make a triangle of your projection and angle it to hit them. Green shells are the best weapon you have. Try to even calculate a double or triple bounce.
Red shells are not that good at close range. Make sure you have a good LONG sight of them, in time and length. If your target goes toward the ramps, its harder for them to hit you there.
Mushrooms are hard to master but if you do you can't lose. Try using them when they come out of a pipe, turning a corner, run into a wall, or something like that when they can't turn or get out of the way. Use if they are sitting at a pipe waiting to be hit.
Bananas can be thrown over the wall, so don't aim to high. Hit the wall then they are going that way and they will run into it.
Use a small car, since big cars are a better target. Small ones can avoid traps, so use small characters like the mushrooms or the babes.