Looking to upgrade from my T7, what's next.

[KD5204]

First the basics, I'm really just getting serious about photography. I think i have a solid understanding of the basic fundamentals of photography but i need more practice. I'm not looking for professional results just really good family pictures that could be printable in standard sizes. I primarily need to take sports pictures for cheer and track and field. I have a T7 which seem to struggle with low light in general. I have the standard kit lenses (18-55/75-300), a Tamron 70-200mm f2.8 DI VC USD, and canon EFS 55-250 IS II. My current images aren't super sharp and are typically very dark (cheer in gyms where lighting can vary drastically between venues) because my iso only goes to 6400. I'll take tips, tricks, advice, tutorials, whatever if it'll help me get better results. But I do feel like I need an upgrade in equipment also but look in the 1000 range new or used. 

[Tintype_18]

Bought a T7 in 2018 and learned to use it with various settings. I take nature photos, baseball, X-country, track and archery tournaments.Took a while but I like to experiment with settings and note the outcome. There are a number of factors with aperture, shutter speed, ISO, lighting settings, etc., that will determine the outcome. You mentioned ISO for the gym but what f stops and lens speed do you use? I downloaded the manual on my laptop with a shortcut for easy access plus D/L it on my phone which takes a while to find what I need. I get bored, get the camera and the manual to look at the various tabs on the menu. The manual and the community, for me, have been a great help. Others will chime in here with suggestions.

[rs-eos]

I would recommend something like the EOS R10.  You would need an EF to RF lens adaptor, but would be then be able to use all your existing lenses.  Over time, you could then move to RF lenses as needed.

The R10 would definintely have better ISO performance.   Definitely use your 70-200mm f/2.8 lens for those indoor low-light situations.

Unless you need to freeze the action, lowering your shutter, especially if using a monopod, tripod, or a lens with IS can be very useful.

[Waddizzle]

Your observation that the T7 tends to struggle in low light situations is spot on.  Part of the problem is that your kit lenses do not have wide apertures.  I would recommend picking up the Canon EF 50mm f/1.8 STM lens while it is still available.  Likewise for the EF-S 24mm f/2.8 STM.