it depends on what is in the soil, but MG has been used before and people have learned what not to do with it. you will probably get more solid advice using that. but for a buck it might be worth it to grab a bag of the cheap stuff and grow a test plant. if it doesn't retain water or gets hard when it dries, add some peat or coco. if you need to improve drainage add some perlite or vermiculite. the pot size is going to be determined by your growing style and how much space you have. 18 oz cups would be ok if you are gong to flower that clone right away. but if you are going to veg you want to use the 3.7 liter (about 1g). transplant, give it a few days to start rooting, then flower that girl.
some basic advice- get more light and improve your ventilation. take it easy on the nutes, especially when using MG soil. if you have the space, lighting and time you will want to top and train your clones to make the best use of your growing area. Read, Read, Read! thats the best thing you can do to improve your growing skills. dont feel the need to try every bloom booster or growth accelerator you see. most arent worth crap. stick to the basics light, water, air, and food.
