The thing with theatre lighting in general is that is quite expensive if you don't have the equipment yourself. Like you mention already, you need to have a USB > DMX interface for Izzy to communicate with the DMX protocol. And you need some kind of dimmer to take control of fresnels / pc / spots or even simple bulbs (That you also need to buy / get somewhere..)
I created IzzyHue, basically actors build in Isadora that allows you to communicate with Philips Hue. I don't say this isn't expensive (still around the 150 dollars mark for the starterskit), but it gives us some options because Hue bulbs can change color, we can change the brightness, we can change the fadetimes, etc.
The reason why I created IzzyHue is because most of the time I'm working on installations / theatre sets and there is not really a cost friendly way to actually change a single piece of scenery. (For example a lamp that we have on the stage that needs to change with the enviroment lighting of the set)
Have a look at meethue.com and if you need any support with lighting in general give me a PM :)