We study the collider phenomenology of the minimal unified version of the supersymmetry breaking scheme called Tree-level Gauge Mediation. We identify a peculiar source of gaugino mass non-universality related to the necessary SU(5)-breaking in the light fermion mass ratios and a gaugino mass sum rule at the GUT scale, 3 M_2 + 2 M_3 = 5 M_1, which represents a smoking gun of this scenario, together with the known tree-level sfermion mass ratio \tilde m_{d^c,l} = \sqrt{2} \tilde m_{q,u^c,e^c}. The boundary conditions of the soft SUSY breaking terms can be parameterised in terms of six relevant parameters only (plus the sign of the \mu-parameter). We analyze the parameter space and define three benchmark points, corresponding to the three pos...