Lens recommendation for my Sony a6700 for pet photography/portraits

So I recently got a Sony a6400 but I’m hoping to upgrade to an a6700 very soon. I haven’t done photography in a while so I’m just sort of getting back into it and I’m very interested in pet photography. I live in a very dog friendly area and I think it’s a great way to get my foot in the door.

I have the sigma 18-50 2.8 lens that I love but I’m wondering what are some lenses I can save up for that would be more beneficial for the kind of work I’m wanting to do.

Open to any and all advice!