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Rearranging Tsiolkovsky gives the mass ratio as e^(dv/ve). Reaching orbit's 9400 m/s on a 340 s engine needs a ratio of 16.6, so a 25 tonne dry stage requires 390 tonnes of propellant - 94% of lift-off mass. That is why single-stage-to-orbit is so hard and why launchers stage.
Mass ratio
m0 / mf = e^(dv / ve), with ve = Isp x g0
Propellant mass
propellant = dry mass x (mass ratio - 1)
Because discarding empty tanks removes dead mass, so later stages get a favourable ratio without carrying spent structure.
Exponentially. Raising Isp from 340 to 450 s cuts the required ratio from 16.6 to about 8.3 for the same delta-v.