First piece of lighting gear
Suppose you're just starting to build a lighting kit from scratch. Right now you're basically using off the shelf home-depot lights and painters lamps, and you're ultimate goal is to have very versitile, and professional lighting gear.
However money is an object, so you're going to need to buy one piece at a time. You want to make sure that you can always use what you have for projects while waiting to get the next piece, so it has to be something you could take into the field and use tomorrow, not have to sit on and wait for the next complimentary piece.
So, you're going to buy your first piece.. What would it be? I'm guessing a good fresnel, But what type? How many watts? etc.
(And what would your second and third light be?)
And please don't just to point out flaws or work-arounds in the thought experiment (like "just rent gear..."). Play the game, and at least answer the question in addition to your other advice.
Assuming you are mostly shooting static interviews, the very first light I would suggest (surprise!) is a Lowel Rifa-light, or a Chimera softbox and speed ring, on either an open-faced light like a Lowel Omni Pro, or a fresnel of similar output like an Arri .
The Rifa is a one-trick pony, but the very best of breed for that one trick, easy and fast to set up and take down and impossible to screw up. If you can afford to get the directional grids for it, do so, but if you can't afford the pricy grids, bring along some cardboard and another light stand to help flag the light. Bring two stands and foam core boards, and you can also throw some fill light with a bounce card and get a 2-light look for the price of 1.
If you go the Chimera softbox/speed ring/spot-flood light route, you will have the flexibility of using the fresnel or open-faced Omni separately for any hard-light application, from bouncing off a wall or the ceiling to raise overall brightness, to making hard keys on talent, to projecting patterns and color on a wall, to lighting up a large crowd, news-style. The softbox and speed ring take more time to set up than the Rifa, but not a long time. The Rifa can run halogen or flo's in case you need cooler running light that draws fewer watts/amps.
Second and third light to get would be the lights you need to do true three-point lighting. That can be fresnels or open-faced instruments. Most of my own experience is in using open-faced Lowel Omnis for everything, treated with diffusion and gels and barn doors as needed to shape and control the light to taste.
If I was starting a kit, I'd get a used Lowel 3-piece Omni light set and case, with a large Rifa, very flexible stuff to use, light and rugged. Will outlive you.
At this point I will still not suggest LED lighting for beginners. One reason is that you can buy used tungsten instruments far cheaper, and they still have more punch and better color than many LED panels. This is always changing, I'm just stating one man's opinion. LED's are definitely the future, but people on a budget should not agree to be beta testers for "immature" technology at a price premium.
Cheap stuff you should also get:
A roll of diffusion, either toughspun or opal frost rolux.
A roll of cinefoil black foil
wooden clothespins and/or metal bulldog binding clips and a heat resistant glove.
Packs of color correction gels, Rosco sells a pack of the most common in one set.
Foam core boards and some way to clamp them.
Gaffer tape and extension cords aka "stingers".
I think Mark's advice is spot on, especially the part about buying used to get started. There are a great many deals coming and going on eBay. The trick is to be patient and not feel that you have to buy without taking a few weeks to get a feel for what things are selling for.
The one addition I would make to what Mark said is Lowel's "Tota-Light." It's basically an open faced tube which, while it looks terrible aimed directly at a subject, is very useful when kicked into the ceiling to pull up a room while still looking like the room's natural light. Tota-Lights are also fairly cheap at around US$125 brand new and considerably less on eBay.
I used Totas for many years; they are workhorses, to be sure, but they get hot and stay hot, a long time. Still, they are better than Lowel "V" lights, the only Lowel Product I don't care for.
In the hands of an inexpert user, I'd recommend the Onmi over a Tota, but each has their place. Safer, more easy to control and get good results, and you won't need as much stuff to flag it off.
I don't disagree, Mark. They DO get hot. Don't most tungsten fixtures? I never use Totas in any situation where there's a need to flag them, though. In my work I'm either using them to kick some light into really big spaces or, as I said, directing them into a ceiling to light an entire room in a highly diffused manner.
I just want to agree about the Rifa. I have the Rifa and an Arri Fresnel kit. Often I feel like I could get away with just the Rifa, a bounce card, and one little Fresnel for most interviews. Like Mark said, using the Rifa, it's hard to mess up. Nice big soft light source. Light and easy to carry. Quick to setup.