Hey buddy,
Im pretty new aswell to the whole permaculture scene. ive been trying some seedball techniques as a guerrilla garden project here in bc..
one thing i can tell you though, is it takes alot of work making seeds balls alone. try to get some help from friends/family..they're gonna think you're nuts, but try to explain to them the concept of seedballs. 1000 sqm sounds pretty big..your gonna need alot of seeds,
compost and clay..
For the seeds, i guess it all depends on your local conditions. here in bc, iv tried a few different seed combos, it seems like the best seeds for this climate are fast sprouting nitro infixing plants like clover or vetch. radish seeds work well too. lupins are a really nice flower that attracts insects and also fixes nitrogen. the wildflower mixes you get from the store work well too for first timers.
Look up sepp holzer and masanobu fukuoka on youtube, just get out there and try it on a smallish plot, with a variety of different seeds, then see which ones grow best.
I hope someone else has somthing more productive to say cus i dont got much else experience..