mate ur going to have to grow sum size of a plant to get 250 grams of dried bud . i normally flower when my plants get to about 1 foot tall and they end up roughly 2/3 feet when finished averaging 70/80 grams per plant . what i would advise u to do is grow small , take clones and and grow 3/4 smaller plants taht u can manage + that make the most of the space u have