I agree with June, a rustic (textured) buttercream finish is gorgeous and not nearly as exacting and time consuming as a smooth finish, a lot more interesting, too. I think the most important step in constructing a three tiered cake is the structure. Don’t skimp on the dowels. I use them to support each tier and, for a three tier or larger, a central dowel through the whole cake anchored into the cake board. It maybe a bit of overkill, but (so far, anyway) I’ve never had a mishap and I transport the cakes already stacked.
Sugar Sugar by SSmiley