Help on growing a plant, not in a garden?

Hi, i'll be buying a plant soon to grow and stuff, i don't mean the seeds, but one that is already grown, but needs more growing know what i'm sayin?So i was wondering if you guys would give me some info, such as which plant is the best ( v.hot country - a desert, but my room has air conditioning and a window from which the sun can ) and should i give it the minerals like nitrates and magnesium and phosphate? How much water should i give it...? thnx :)