billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

You did not mention your camera. Most of today's camera's can produce excellent results to and iso of 6400 or a little higher. Do not use flash, I am surprised you have not been asked to leave.
Also, shoot from the floor at one end of the floor. You will get better shots that way.

kibbles304 Loc: Indiana

I am a hack photographer shooting my grandkids in grade school and middle school gyms (bad lighting). I did the best I could with the Nikon D7100 w/Nikon 50mm f1.8 and Sigma 70-200 f2.8. I was finally able to get a refurbished Nikon D500! What a difference! Being able to use a little higher ISO was a big help but I was so surprised what the anti-flicker setting did for getting the right WB was just amazing.

TriX Loc: Raleigh, NC

Simple equipment answers for indoor sports in poorly lit gyms:

fast lenses (f2.8 minimum, faster is better)
cameras that perform well at high ISOs (6,400-12,800)
good performance AF set on continuous focus
Anti-flicker is helpful
Usually NO FLASH

Unfortunately, this particular genre’ is one of the more demanding in terms of equipment.

ELNikkor

Wouldn't use the flash, set for 1/250 or 1/500 of a second, and do some test shots at f4 to see what ISO is necessary to get a well- exposed image. You need that high speed shutter to stop the action. Forget about the noise; it may be the price you pay for the low-light, and it is possible to find a program that will "denoise" it for your favorite shots in the computer. Good luck! Let us know how it goes and send us a sample of your favorite shot.

Flash Falasca Loc: Beverly Hills, Florida

WHAT is line frequency syncing feature, does it haveto do with the 60 cycle electric lights ??

Toment Loc: FL, IL

TriX Loc: Raleigh, NC

Yes. Incandescent lights aren’t especially noticeable as the filament tends to smooth out the fluctuations, but the output of discharge type lamps, which have a faster “response” (including fluorescents) varies with the 60 Hz (in the US) line voltage, with a minimum at the zero crossing and a maximum at the top or bottom of a cycle. You don't see it, but at faster shutter speeds, the camera does. If you shoot a fast burst under that type of lighting, you can see the variation between frames. The flicker sync feature syncs the shutter with the variation of the output of the lamp, keeping the exposure relatively constant.

Dond

I shot a lot of basketball games in the days of film when we didn't have high ISOs and good lighting so I had to use flash. The way that I did it was to set the camera on manual at the maximum shutter speed that the camera could use to sync with the flash (looks like 1/200 in your case) and at an f stop that would work to illuminate the subject at the power that my flash could produce at the ISO of the film. In your case, you might start at ISO 400, f5.6, and 1/200 sec. The flash should be on "auto TTL", if its an external flash. The duration of the electronic flash's flash will be something like 1/600 sec. or faster so the flash will top the motion rather than the shutter speed. Of course, because your settings are such that ambient light won't expose anything, you'll only have the player(s) illuminated in the photo.
I agree with the others that one shouldn't use flash at games because of the possibility of interference, etc. but, if you have to because your lighting and/or equipment can't support the available light option, then this is how you can do it with flash. Usually the players are so intent on the game that they don't notice the flash.

PHRubin Loc: Nashville TN USA

Same thing as the anti-flicker setting. Yes - for the 60 cycle (US) or 50 cycle (Euro) lights.

rehess Loc: South Bend, Indiana, USA

The best solution remains more light, which traditionally was obtained by using f.2.8 or f/2 lenses. Lenses like that tend to be fairly expensive. Recently, another solution is to make better use of the light you do get, such as a Nikon D500, Nikon 750, Canon 1Dx, or a Pentax KP.
https://www.uglyhedgehog.com/t-631428-1.html

jamesl Loc: Pennsylvania

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I'm not sure how well it would work in your situation, but if you are allowed to use flash, try using high speen sync if your camera and flash support it.

charlienow Loc: Hershey, PA

I would assume you use auto iso with this setup?

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

In a gym you need a camera that can give you reasonable image quality at ISO 3200-6400. The camera needs to have an anti-flicker mode so you will have even lighting across the frame, and if using a superzoom lens, which is usually F5.6 or smaller at the longer focal lengths, you may need to kick your ISO even higher.

A better solution is a faster lens that you can shoot at F4 or even wider.

Many cameras support high speed sync with flash, so you can shoot at 1/1000 or faster, but at the expense of output power and much longer recycle times - not ideal for sports. Besides, using a flash is a terrible idea, as others have suggested, since it can interfere with the players' vision.

joer Loc: Colorado/Illinois

This lens is only 3.5 at the short end. I'm surprised flash is allowed, but if you can use it, don't worry about the sync speed, the flash pulse will stop any action. Set the shutter somewhere between 1/60-1/125, flash at TTL or equivalent and auto ISO. And use a noise reduction program.

amfoto1 Loc: San Jose, Calif. USA

First thing you need to do is get and use a faster lens such as a 50mm f/1.4 or 85mm f/1.8 or 100mm f/2.

Your lens is f/3.5, nearly 1.66 stops slower than f/1.4... but that's only at the 18mm setting. It's undoubtedly a variable zoom that stops down at longer focal lengths. It's probably f/5.6 or f/6.3 at 300mm. Maybe f/4.5 or f/5 at the middle focal lengths. For example, f/5.6 is 4 stops smaller than f/1.4... what that means is that f/5.6 only allows 1/16 as much light through the lens, as f/1.4 does. So first thing you need "faster" lenses... Lenses with larger apertures that capture more light!

You also can increase your ISO until you can get shutter speeds of at least 1/320 or 1/500, to have any hope of "freezing" the action. Even faster would be better, if possible.

Assuming the gym lighting is "typical", it also probably is sodium vapor or fluorescent, which rapidly cycle on and off (60 Hertz in N. America, 50 Hz in many other parts of the world). This cycling of the light is so fast (120 times per second) that our eyes and brains don't see it, but our cameras sure do!

The result is that a high percentage of your shots will be seriously under-exposed. Unless you have certain cameras, there's not a lot you can do about it. Most current Canon DSLRs and mirrorless cameras have a feature called Flicker Free that detects the fluctuation of the lighting and times the shutter release to coincide with peak output. This works really well. Some Nikon models have a similar feature. I don't know about other brands. But you should check your camera and see if it has this feature.

Another common problem is the "color" of the artificial light. It can make for really ugly colors in your photos. The best way to overcome that is to set a Custom White Balance with your camera. That's pretty easily done, check your camera manual. (It may help to have a special "fluorescent" target to use when setting the Custom WB... such as is included in Warm Cards. If your images look greenish, that will help offset it and make for nicer looking images.)

Flash is a bad idea shooting sporting events (like some others, I'm surprised no one stopped you from using it).