Outside of the limited medical program, the purchase and sale of cannabis are not legal here on an adult-use basis. Although it is legal to possess or gift cannabis, there is no actual adult-use industry.
Many stores will "gift" you cannabis if you make a qualifying purchase, but these stores are far from acquirable or financeable. A recent bill was proposed to ramp up enforcement against the District's unregulated cannabis businesses, but the votes fell one short in needing to pass. The program is as ass-backward as they come, but for now, if you find the right store, you can pay $10 for a sticker and walk out with a dime bag.