I would go with pellets first. In my experience Diablo Field's will be consistent in any HW....not so cheap at around 11 quid.
They also work well in my Brocock PCP pistol which is very sensitive to pelet quality.
Tried many pelets in my HW100 and 97, and the only one that gives me consistent pelet on pelet is the above.
I'v never resorted to lube unless I'm having a special nite in