hiya Idolovegreen, too many variables to give you a proper Answer...
All I can say is start with maybe 3~4 and pick a Auto Strain that is a (Reportable) a Good Yielder..
Maybe take a look at Herbies? I picked up some Cheap Auto's from there(But these just for Trial & Error Run) but these are Auto Regs..so you would have to pull any Males...cheap way to learn though(But probably NOT the best for Yield)
KC Brains KC45 Autoflowering Seeds(REGS) = £10.89 + Pnp
Link to Page > > > >
http://www.herbiesheadshop.com/autoflowering-seeds
Welcome to R.I.U. and Good Luck...
Also check out the Auto section of site and see what others say about this strain OR that strain...
Peace