for the beta ark the standard is 130/60 front & 140/60 rear.
however if you want a sportier look you go with a 120/70 front but keep the rear tire size as it is.
Pirelli Evo21/22 are the best tires out for 13" wheels, i haven't tried the Metzeler ME-7teens yet but maybe on the track on Nov16 (Inside Racing trackday) at carmona.