Heya,
With $200, I would go with a single good light. Speedlites are great, portable, and run outside with you. You don't need much to get them working. If you plan the day and use them in early morning or late evening light, they can be powerful enough to handle those situations (but they're limited in full sun except at extremely close proximity to subject).
Before you get into speedlites, I would suggest you do a little reading on your 70D though; it's known to have an issue with ETTL bounce exposure specifically, and that's going to be quite similar to off-camera lighting work. You may want to research this and test it before getting into something (specific to ETTL and bouncing off a surface, not direct flash). If you're shooting manual, it won't matter. Just something to know about.
Stand:
I would get a good stand, with a boom arm. Sometimes you want your light above the subject, but not in the FOV from your perspective. Booms do that. Don't skimp on your primary stand. You need a good, stable, strong stand to put your light where you want it. It's going to be close to the subject, so you'll want a boom to be able to move it around and position it, closely, without having to dodge the center column in your FOV.
Suggest: This stand
($89) - This is cheap for what it does.
Speedlite Mount & Modifier Mount:
There are cheap things out there that hold a flash. But I'd suggest you go with something strong, holds the flash well and safely, doesn't stress the shoe, and has two modifier mounts (bowens and umbrella) so that it can be adaptable for you. S-Brackets do this.
Suggest: Godox S-Bracket ($20)
Modifier:
Starting out, I'd go with a simple umbrella or a brolly box (umbrella style softbox). They're inexpensive and very good. Light weight. An umbrella will spill more light around it. A softbox will control spill a little more. Just depends on what you're going for and how much control you want. I'd get something in the 43~48" range. Bigger is softer relative to the subject, so a big source near your subject produces soft light. Also, a bigger modifier will allow you to light up more than one person from a distance without it being too harsh of light.
Suggest: Westscott 43" Umbrella ($20) | or 47" Brolly Box ($35)
Speedlite:
Picking a light is more than just the light, you want to pay attention to the communication system too, since you're going off camera. You want a communication system that is broad and works with lots of things and doesn't block out potential lights in the future from use, then you end up rebuying stuff. The R2 system is pretty great and very all-encompassing. You can't go wrong with it. That way you can grow your fleet of lights in the future and doesn't matter if it's a speedlite, strobe or whatever, the R2 system will command them all. Also you want a light that has a built in wifi receiver if possible; less batteries, less stuff to get, the newer systems have these, so go for that for sure. That means getting a single transmitter (R2 system) to talk to everything from the camera, so you'll be getting just one. From there, you could go with manual lights. Or you could go ahead and get something with ETTL & HSS so that you have those options whether you use them or not. Outside, you'll probably want that HSS option. And sometimes you may want ETTL for when you cannot setup a shoot and just take spontaneous shots. It's better to have the option than not. I use all manual lights, but I always keep a single ETTL/HSS capable flash in there so that I can use it on-camera for spontaneous stuff that cannot be redone. Very useful with kids! I'd look at the Godox R2 system. You can get it under Flashpoint as a rebrand from Adorama.
Suggest: Flashpoint (Godox) TT685C ($120) & Flashpoint (Godox) X1T-C ($49)
$300 budget. But no cut corners. All good reliable stuff. Lots of room to grow.
Then, to grow the system, just add more R2 system flashes/strobes. This flash can be used in every way you can think of. On-camera. Off-camera. With ETTL/HSS, or just go manual. It will get you all the potential to learn. Even if you move on to bigger strobes later and go nuts, this flash will still be super useful on your camera for ETTL/HSS spontaneous shooting in the light with kids outside.
You can then add manual lights on the same system for an inexpensive cost, that have wifi receivers and work on the same system (R2): Flashpoint R2 TT600 ($69) a piece, so you can flesh it out to 2 or 3 lights as you wish. Or more.
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If you end up wanting to add a powerful strobe for outdoor HSS work, budget will need to increase significantly.
Strobes indoor, even cheap ones, can be great because you don't have to have batteries, etc, and can get powerful light for big modifiers on the cheap. But, they will be wired, no ETTL/HSS (not needed inside anyways really). They can be very useful though simply for lots and lots of shooting being wired instead of on batteries. So if you see yourself going this direction ever, or even now, this is another subject to expand upon.
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Example of why I stress a good boom stand for your speedlite for creative control:
IMAGE LINK: https://flic.kr/p/tUo5r3 IMG_7882 by
Martin Wise, on Flickr
IMAGE LINK: https://flic.kr/p/uhA1V4 setupshot_cellphone_stalker by
Martin Wise, on Flickr
Stopped down ambient with 4 stops of ND filter (I didn't have HSS, this is a basic manual speedlite). But, at very close range in a larger modifier, you can get soft light even in sun. Boom gets it out of the field of view and close to the subject, without an assistant.
IMAGE LINK: https://flic.kr/p/tUudze IMG_4179 by
Martin Wise, on Flickr
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Or, basic on-camera use, with ETTL & HSS employed so that you can combat sun for fill flash without looking flashed (ETTL & HSS together is really, really awesome and allows you to do things with no 2nd chances):
IMAGE LINK: https://flic.kr/p/RY2uDo IMG_5208 by
Martin Wise, on Flickr
Very best,
