Indeed, i would do Oak Larders till 55. But, asking how to train the skill here is a bit dumb, the real estate people explain everything, don't just spam click to continue with a new skill >.< Basically, you make things for xp, sometimes using nails, a hammer, a saw, planks, limestone, marble, steel bars, all sorts of things, have a look at tip.it's construction guide for more info.