I may not be able to help very much, but I will try. what type? green? red? I don't think you can get a blue laser for $30. what do you plan on using it for?
I would recommend around 200mw to see the beam and pop balloons (and light matches and cut tape and melt plastic, you get the idea) but anything above 5mw YOU NEED GLASSES FOR! it is extremely important! this has A good summery:http://laserpointerforums.com/f53/general-safety-help-51877.html#post721040