What is a good ammount of mod elements to release a mod at?

There is probably no number to define this, it depends from mod to mod. But keep in mind that it can be quality over quantity in many cases ;)

150-200 is enough to get MOTW I think , since I already got MOTW 3 times with mods about 200 elements each

you can probably get motw with just 10 mod elements because i think the chose a mod on how well made it is, like klemen said quality over quantity.