Yes, you can try doing that with the MG and the soil, but I don't know if it will like it or not. If you have no way to get better soil, I guess it will have to do.
When you transplant, try to do it when the soil is not too wet, and not too dry, but right in the middle.
Try to pick the spot that will get the most sun during the day. MJ likes to have lots of full sun! Once you have a place to put it, dig a hole in the ground and mix in some MG, make sure you mix it up well with the existing soil. You should try to dig a hole at least 1 foot by 1 foot by 1 foot deep. Once you have the hole dug and the dirt prepared make a hole in the middle of your good dirt that is a little bigger than your pot. Since your pot is not full of dirt only make it as deep as your pot is full. Set the dirt to the sides of the hole so you can push it in and around the plant that you're going to put in there.
Now bring the pot with the plant in it over to the hole. Squeeze the sides of the pot gently all the way around to loosen the soil's grip on the sides of the pot. Then put your hand over the top of the dirt with the stem of the plant between your fingers. Next you need to turn the pot on its side and try to get the root ball and dirt to come out of the pot. You may have to turn the pot completely upside down, but with your hand in the correct position covering most of the soil with the stem between your fingers you can hold the plant this way for a moment. Just don't grab the stem and pull up on it, you will risk ripping it out of the dirt that way.
Get as much of the original dirt to stay on the roots as you can, and stick the whole root ball into the hole you made earlier. Try to make sure the stem is straight up, and at the correct level with the ground, and gently pack the good dirt in around the plant. Make sure to press down gently all the way around the plant until the soil feels pretty firm. Don't push too hard, you just want to make sure it isn't going to float away when you water it.
Next, give it some water, and if some of the dirt sinks in around the plant anywhere, put more dirt in there to make it even at ground level all the way around the plant. You should water it at least once a day for a few days after you put it in the ground to help it survive the transplant.
I can't guarantee that this will work if the soil is as bad as you say and you are using MG, but it is a weed and outside in the sun it will grow as long as something isn't horribly off. When you are getting the MG, try to get the Organic version or some version that doesn't have time-release fertilzers in it. Also, if you have someone who can help you that has transplanted a plant before, sometimes it is easier to watch someone do it than to try to read about it and do it by yourself.