Just want little bit share my experience.
Now I'm participating about 18th of airdrops and giveaways all together. So now is the best active airdrops - bitsend (maybe 17 coins per week, bitsend available in exchanges), I like liteshares (just one guy open it, but I hope it will be like bitcoin-litecoin), possible to receive netm. And you can try bitrad.io, but I think it quite late to earn coins by listening radio (available in exchange)