Light choice also depends on what you're using for camera/lenses. if they have x-sync, then monolights are a good choice. If you have no X flash sync (such as pre-WWII LF, then hotlights or existing lights are your options)
If you want to take existing light as far as you can, get a reflector kit also. Lets say someone is side-lit at a window. you can use the reflector to vary the shadow strength, or the gauze layer to diffuse bright beams. Something like the 5-in-1 reflector from wescott. This is my most useful lighting accessory. It work indoors or out in any situation except high winds.
For doing what you can with two simple hot-lights, read Mortensen's "Pictorial Lighting". A good teacher and photographer. These skills translate to monolights as well.
I have monolights (old white lightning units) which are handy and do a good job, but I can't use them with my most ancient equipment. So I have some aluminum dish worklamps from the hardware store ($7-10) with CFL bulbs in them, and I have a couple LED panels ($35) from ebay that are sold as grow-lights. Monolights are great for lighting a whole group or a whole room because they make a lot of light, but I rarely have to do that. If you use strobes like monolights, you will also need either a flash meter or DSLR handy to determine proper exposure. You can't figure that stuff out in your head like GN from a regular shoe mounted flash.