I’d recommend checking out the sigma 150-600mm lens. I think it’s compatible with your camera and should give you the reach you’re looking for.
Do you have any interest in going out for your birding? In which case I might recommend a monopod for a little more maneuverability and I personally wouldn’t use a gimbal for this. As for compatibility I think pretty much all tripods/monopods are fairly universal.
Another option for some savings would be to find a 2x teleconverter for your camera so you can push up to 400mm. That plus some patience should get you good shots, especially if you go somewhere you know you’ll find a lot of birds. Heads up though a teleconverter isn’t magic and will always have a cost for that increased range. They basically only work in strong light and sometimes affect the quality of the photo (sharpness) depending on the quality of the glass.
For reference I’m an amateur photographer who mostly does birds and a little astrophotography. I’m new to this whole federated social media things so I’m going to uploading my work over the next few months. Always happy to talk photography!
Awesome! I need to figure out how to do good astro but I’ve got so much light pollution.