If you are a medical patient then you should know what strains help with your particular condition so one of them, one that you feel works the best, is what you should grow, isnt it?
If you have a medical condition and you will be growing your own medication asking other people what they think you should grow is not the best route to take. Even if you wanted the opinions others for what they believed would be best for you then you should mention your medical condition so possibly someone can pick the proper strain or strains for your condition.
It is not like one strain will be super easy to grow and another will be really hard to grow so first time or not you should not pick anything other than what will give you what you need the most. Sure you will likely make a mistake or two but you might as well learn on what you need the most instead of learning on something that someone else tells you to grow that will not help much if at all with your particular medical condition.
As for using a HPS for flowering and vegging maybe you can find a metal halide conversion bulb that will run off your HPS ballast and that way you can have both light spectrums for just the additional cost of a conversion bulb and not at the cost of a full second light setup.
Good advice.. I was focused on what I had actual experience with, but yeah...
A lot seedbank sites do have "medical" sections, and usually comment on "easy-med-hard" for growing. I do think there is some differences among strains that, for experienced growers, are no biggee.
But, if this is going to be your first time growing MJ, I'd suggest getting something clearly described as easy. I've grown everything under the sun except MJ til recently and I can tell you, it definitely does have its own funny little quirks that you need to learn first-hand. You don't want to complicate that with a touchy strain, and there are some.
Just my 2 cents, being on the backside of my first grow..