Generally, I bring an amount of gear inversely proportional to the mobility of the photoshoot. A "standing photoshoot" where I'll be with cosplayers at 1 single spot will have me use more photo gear than a "moving shoot" where we'll hit as much as 5 or 10 locations in an hour, depending on our pace.
One thing's for sure, the more gear you bring, the longer it takes to set it up at the beginning of the shoot and wrap up at the end. This is feasible for "standing shoots", but for "moving shoots" it's more tedious as you'll have to do it for every location you hit, costing you some time.
In case of doubt, bring your whole gear (as for a "standing shoot") and only deploy what's needed according to the mobility of the shoot (the number of locations you'll hit with your cosplayers).
Oh, and this is the best tip ever... Use a photo assistant! Helpers can speed up the setup and wrapup times of your gear, leaving you more time to take photos, taking more shots during the shoot, getting a higher number of "keepers". The helpers can also move stands for you and hold reflectors, as well as help the cosplayers to drape their dresses and capes. Additionally, they can suggest pose ideas when the cosplay photographer and cosplayers run out of them, and watch everyone's belongings, to deter theft.
Personally, here's what I use:
- 2 x Speedlites
- 1 x low-cost wireless flash trigger set (transmitter & receiver)
- 1 x small softbox
- 1 x small diffuser
- 1 x tripod
- 1 x lightstand
- 1 x shoot-through umbrella
- 1 x umbrella bracket to mount a Speedlite & umbrella onto a stand
- 1 x 5-in-1 reflector
- 1 x small flashlight (to help auto-focus in the dark)
This is my full gear that I bring to "standing shoots". Knowing
I'll be at a "moving shoot", I just bring the 5 items on the top of the list. Not knowing if we'll move or not, I bring everything with me and deploy/use items as required.
I also shoot at photo booths. While the backdrop is usually already supplied to me, I'll bring all the gear above plus 1 x monolight strobe, 1 x powerbar, 1 x extension cord, 1 x silver reflective umbrella and 1 x lightstand. The umbrella mounts into my strobe without the need of an umbrella bracket. Of course, I don't bring my strobe to an on-location shoot, as a power outlet might be unavailable where I'll be, or if there's one, I won't be allowed to use it.
you'll be at a spot with lots of space, you should bring longer lenses for portrait shots. Knowing
you'll be in a tight spot, you should bring wider lenses. Not knowing how spacious the shooting location will be, you should bring zoom lenses to accommodate for different types of environments.
Having lenses with apertures of f2.8 or larger is strongly recommended, especially in low-light areas. Prime lenses (50mm f1.8, etc) will do a great job, but often requires you to move around, which is sometimes not possible with certain areas, depending on the focal length of your lenses you might often be limited to taking only upper-body, bust and head shots. Of course, having an assistant with you can ease up the change of lenses.
You should bring an extra set of AA batteries for your Speedlites. The first Speedlite who runs out of battery power, you switch them with the set of charged ones. It's rare to have to change batteries twice during an 1-hr shoot. Also, it's faster to shoot 2 Speedlites at 1/2 power to get 1/1 power than to shoot 1 Speedlite at 1/1... Just a tip.
Your helper must be in sunlight, even if this means standing more than 20 ft away. (Bouncing blue sky light is not effective at all.) If possible, move your cosplayers closer to the boundary between shade and sunlight so that the distance from the reflector to the subjects is reduced. Watch out for wind. Also, the reflector can be used to create wind, blowing the cosplayer's clothes and wig for a nice windy effect.
Wind is the umbrella's #1 enemy. Have a helper hold your lightstand + Speedlite + umbrella. When in the wind, an umbrella acts as a sail, applying torque onto the lightstand, making the whole stand tip over and fall. Usually, the umbrella will take the brunt of the impact shock with the ground and your Speedlite will be safe. You'll have to buy a new umbrella then, but most of the time your Speedlite will have no damage from the fall and will continue to work properly.
If it's really windy and you have no helper, then don't use an umbrella. You must have someone to hold your stand; a sandbag or backpack is usually insufficient.
Softboxes are less wind-prone, but they're not wind-proof nonetheless. Don't be careless when you're using a softbox outdoors, as a strong-enough wind may knock your stand down. Light breezes won't do much, but strong gusts can displace anything.
Normally I would shoot in RAW for random hallway shots. But for scheduled private shoots, you have more control of the lighting and placement of your subjects. It would be OK to shoot in JPG in this case, but I shoot in RAW to maximize the adjustability of my source images (I can usually output 2-3 different final images per RAW). Shooting in RAW+JPG is also OK, but would require a lot of memory card space, and bursting (continuous shooting) is severely limited, as the camera needs to save to the card all the shots in its buffer before letting you resume shooting, which could take several seconds.
Don't forget anything behind:
It may happen that, between 2 shoots, you'll forget something behind, like a tripod or a Speedlite. Make sure you have everything when you wrap up, and ask your helper to confirm that you left nothing behind. It's costly to replace a forgotten/stolen item (especially a Speedlite), or time-consuming if luckily no one stole it.
So look around you before you head to your next shoot, as this will save you money from having to re-buy a certain piece of gear or save time from running back to your previous shooting location to retrieve the item you left behind.
I hope this answers your questions and any other that you may have!
FYI, I have a Canon Speedlite 430EX which is synced wirelessly and a Yongnuo Speedlite YN467 which is synced optically. I also have a hotshoe sync cord for TTL flash. My monolight strobe can be synced optically or wirelessly.