Hi,
I used aliexpress affiliate program last year and got dissapointed. Since september 2015, they cut off the 30-days cookies and from that moment sales dropped from 50/day to 2/day. Now their program is session based, as soon as potential customer closes his browser, you can't earn from his purchase (unless he follows ur affiliate link one more time and makes a purchase).
At the moment I think amazon offers better program, they offer 24hr cookies, and if you target USA or UK you can make fine sales. Commisions are about the same (~8%). I became amazon associate few weeks ago and by now I made 33 sales resulting in ~400$ earnings.
I must add this - google is not a fan of our affiliate websites. I use email marketing + a few blackhat methods to get my website some decent traffic and a few sales daily. U should be 80% concentrated on products which have price range 150$-400$ and 20% concentrated on cheap products. Cheap products are selling more frequently and can get you higher commision rate at the end of the month. Use social media, it's also a good way to get traffic (and with more traffic more $$$ is earned).
I hope you find some of those information helpful on your journey, cheers!