soil options for one time attempt?

Long story short, one closet with a hydro setup got crowded, so i moved a jack flash into another closet to keep vegging while the crowded closet flowered.

Only have one hydro setup, so the flash was kept in the rockwool and put into some happy frog soil and have been using lst for around two months. Very happy and big bushy girl, but its about time to throw it into flower.

I am not very knowledgeable about soil and I am looking for a low cost soil mix i can use for flowering this one plant, hopefully not have any leftover, and wont have to buy any nutes.

If I do a fox farm mixture like light warrior/ocean forest will I need to add anything but water/molasses?

Is it cost effective to make a small amount of mix of something like subcools soil mix?

thanks for droppin some knowledge. any recommendations or options are appreciated.

plagron bat mix is good for flowering, ive gone 8 weeks and only fed molasses, and a bit of magnesium sulphate, once in week 6

pot size is important, you will need at least 15ltr to go 8 weeks (about 4 us gallons).

Yeah I was going with 5 gal or 8 if there is the option for it at the store.