how to choose graphite pencils for realistic shading on toned paper?

i'm an art student in india, been messing with toned paper for the past 3 weeks and posting progress on reddit, but cant get lifelike shading. i bought a cheap 5 pencil set and tried 3 grey sheets, everything reads flat or muddy and my highlights vanish. i dont really get which grades to pick, how many pencils i actually need, or whether softer leads or a bit of charcoal will help, plus im clueless about sharpening. exam in 2 weeks, feeling stuck, anyone who knows how to choose graphite pencils for realistic shading on toned paper, pls help.