you dont need much food for now.
they live off the soil.
you could get some vegg nutes, but they are not really needed, unless you are vegging for a long time.
use molasses or castings,blood bone meal.
even m.grow,or tom food, 1 time a week, but not for 12/12 get some proper nutes for 12/12.
how long are you planning to vegg?.
when i 1st start to grow with a small seedling, it dont need feeding, it feeds from the soil for the 1st 4 weeks or so and by then i will have repotted. so it ok for another few weeks with the new soil, till its time to flower.