I use this kit,
http://www.eoslightingllc.com/filmmakers/tungstenkits/3250/.
If I may...good lighting incorporates things like color temperature (in-door/out-door), lighting ratios (high key/low key - this is to your question of using diffusion) and exposure. But most importantly to achieve good lighting one must also always be aware of the intent, or to put it more accurately, the motivation of your lighting.
When talking about 3 point lighting people tend to get wrapped up in the whole "you have a key, a fill and a back light". I used to be obsessed with where these three lights should be instead of considering the most important aspect of lighting, which is getting the lights to do their job without them being noticed. Regardless of the tools used (i.e., natural, Home Depot DIY, bounce cards, professional lighting kit, or a hodge-podge of any number of the above) your goal is to make your lighting appear as natural as possible. By natural I mean, your lighting should be able to replicate the effects of the sun, a light fixture or a given practical without being noticed all while providing you with enough light for your desired exposure settings, mood and subtext.
Also remember to maintain continuity with your coverage. Make sure your lighting ratios, angles and shadows remain consistent as you move in with your shots. Sometimes some cheating will be involved (moving things around on the set as you move in for coverage) but as we all know continuity is a must, that is if you want to have an easier life during the edit.
In conclusion my ramblings all come down to this, regardless of the tool (light source) and technique (3 point, head-on key, side lighting, etc.) remember that your goal is to have your lighting appear to be natural and consistent from shot to shot.
I hope this helped.