Without getting into true telephoto design, your camera will support 500 mm at infinity. Less then that if you do any close up photography. Myself, I would not consider much above 400 mm in a non telephoto lens for the reason of close up bellows extension. This would give an equivalent of roughly 130mm in 35 mm.
With a telephoto design, different then what I was addressing above, the focal length could be increased but in telephoto designs focusing considerations as relates to lens standard tilt changes. They are more difficult to work with, for that reason, in my experience.
Which lenses? That depends on whether you are buying new or used. The Nikon Tele designs are popular. I like the G Clarons in Schneiders non tele designs, tons of coverage and sharp as a tack at a fairly reasonable price.