The rocket equation is dv = isp * g0 * ln(m0/mf) [1]. For dv we assume 10% the speed of light, isp of a ion thruster is say 19300 s [2], for g0 I will use 9.80665m/s^2 and mf is 1kg. For m0 this gives us m0 = mf * exp(0.1 c / (isp*g0)) = 6.2e69 kg. The (baryonic mass) of the observable universe is something like 1.5e53 kg [3]. Or in other words about a factor 4e15 (much more than the 2e9 the grand parent poster claimed) less then the necessary fuel.

1: https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation 2: https://en.wikipedia.org/wiki/Ion_thruster#Comparisons 3: https://en.wikipedia.org/wiki/Observable_universe