For these subjects, a telephoto lens is the main need—not a teleconverter. Teleconverters usually require compatible longer lenses and often reduce light, which is a problem for indoor sports.

On the EOS M50, indoor wrestling is the harder job because gyms are dim and action is fast. A lens with a wide maximum aperture helps most indoors. Football from the stands usually needs even more reach.

A practical budget approach is:

• For football: a telephoto zoom, roughly in the 55-200mm or 70-300mm range.
• For indoor wrestling: prioritize the fastest telephoto you can afford, because shutter speed matters for sharp images.

If you want one lens to start, a telephoto zoom is the most flexible choice, but budget zooms may struggle indoors because they are not very bright. If wrestling is the priority, consider a lens that lets in more light, even if it has less zoom range.

Also learn the basics of shutter speed, aperture, and ISO. For sports, use a fast shutter speed and continuous autofocus. Clear results will depend as much on technique and gym lighting as on the lens.