Unless you're playing basketball ~3 times per week or so youll definitely make your most gains just by getting out and playing basketball. Regardless of the sport you put someone into an unfamiliar movement pattern and they'll soon be coughing up a lung. I see all these guys sparring one day a week and want to throw all this fancy conditioning in with circuits and stuff and they wonder why it doesnt work well. Regardless of how "inshape" someone is the first time on the court in a while is a torturous experience.
Also if your aerobic foundation is not developed at all you can get decent results just doing regular LDC a few times per week for 20-30 min, as it serves as the foundation to anaerobic endurance. See McLaughlins stuff for further info. The intervals will work for a couple of weeks but they're more like a cherry on top and will burn you out if you're not ready for them. I'd start off with 3 sessions of activity per week and work from there - it could be 1 game and 2 coditioning sessions or 2 games and 1 conditioning.
One other thing I would consider at your age is a reduction in weight training volume and an increase in mobility work. You can train heavy but I wouldnt suggest training to the point where your legs are sore all week long. Get your movements and movment efficiency back in order first until your body starts to feel "good" on the court then start hitting the weights hard.
