hey, this is my first grow ever.I’ve just bought 3 x ww autoflowering seeds from ILGM team.I will use 19 LT pots per plant and biobizz lightmix soil and biobizz grow and bloom nuts.How much yield can i get per plant ? oh btw lighting is 250 w hps 24/0
Impossible to say 
Being your first grow you will possibly put your babies through some hardships like heatstress, over/underwatering, nutrient issues etc. Everything that give your plants stress will effect yield.
If you treat them reasonably well I would take a wild guess at maybe 10-30grams each with that light…
I will use instructions on Biobizz website for nutrients 
how much watering per 2-3 day ? i read over a website 330 ML per every watering ?
Start lightly with the nutes at even lower dosage than stated by Biobizz. Autos are sensitive to nutes and should be fed lightly early on. Even with the Lightmix you would want to wait 3-4 weeks before feeding at 1/4 strenght.
Okay thank you. so as a summary with light mix soil Will I wait 3-4 weeks before feeding ? with 1/4 do you mean 0.25 ML per liter ?
Disregard my last post, that was not with the Lightmix.
I’ll send you a link of an informative growlog