how can i make a toy plasma thruster that actually works???

Here I found this: http://myelectricengine.com/projects/mpdthruster/mpdthruster.html
Hope it helps.

OK So i read this but i got a question, Is the high voltage only needed to start the rocket or is it needed through the entire reaction?

My understanding is that you want to make a larger scale plasma thruster, presumably for some kind of rocket. That being the case a plasma rocket motor is easy to construct, but dangerous to operate.

First you need some kind of fuel to ionize. Air is convenient and plentiful. Just having air is not enough. You either need to have a blower, or a compressed air source to keep enough air flowing that the plasma stream won't move and eat your rocket.

Now that you have air, you need a high voltage continuous power source. By high voltage, I mean several hundred volts to start, many plasma torches use 400vdc.

Once you have air and power, you need a nozzle to handle the air and voltage and survive the plasma. If your rocket cannot contain the plasma for any time, it will just catch fire, and maybe explode. In many plasma torches they use an electric spark fired from an electrode into the grounded work surface to create the plasma. Air is injected twice through this nozzle, once through the spark to ignite and create plasma, and once AROUND the plasma to keep it from eating the rest of the nozzle. This also serves to keep the nozzle cool and not melt so fast.

You cannot use that method, as you have no grounded surface to touch. That being the case, you need to create a spark perpendicular (Intersecting at a right angle) to the flow of air. This will cause the air to ignite into plasma, and expand like fuel dumped into a jet engine in afterburn. The longer you can contain this plasma, the more thrust it will provide.

Please understand that plasma WILL try to get away from you. It has high magnetic fields and they are pretty random. This will "Push" the stream in different directions, and so this is inherently dangerous. If the plasma makes contact with any surface, it will eat it rapidly.

 Plasma Thrusters more commonly known in the world of science as Magnetoplasmadynamic Thrusters use the hall effect 

I never knew you could make something as cool as that yourself. I always assumed plamsa referred to a plasma television rather than the negative ion generator above. Quality.

ok its called a negative ion generator i do believe....here is how it works...i think... the air coming in is + air the current flowing through the generator is a negative thus attracting the incoming air....this is how the ionic breeze works the downside is this produces O3 aka ozone but not enough to do any damage...unless you lock yourself in an airtight box for a week...anyway it barely produces any "wind" whatsoever but is nice to have cause when you turn off the lights it has this cool blue light...here is a link to my friends touching the high voltagehere is a link to my friends touching the high voltage..idiots...actually their my friends

plasma is a more or less expanding gaz. producing it in a tube with one end blocked produces thrust, albeit not as much as chemical fuel (h2o2). any high voltage source (such as an aic or marx generator) will work.

Here!
http://www.rischenterprizes.com/plasmathruster.htm

A pair of electrodes connected to a high-voltage supply arc across a flow of water.

The water is zapped into charged plasma, flowing between the electrodes.

Under the white material (a sheet of PTFE) are a pair of magnets. The charged plasma is pushed by the magnets in exactly the same way as a charge-carrying wire is pushed inside a motor.

All of which you would have found if you had followed the link to the thruster maker's site.

For a similar process that uses lower voltage but achieves vaguely-useful thrust is the magnetohydrodynamic effect (sometimes known as a "caterpillar drive"), which uses water in the place of plasma.

Like this little toy from EMS: