The easiest way to learn a second language is in the home from infancy. If you're really motivated to promote an international language, you should have some kids and teach them Esperanto from birth. That being said, plenty of people around the world are already learning English as a second language, whether in school or by choice. I think it would likely be easier to reform English to be more consistent. Dough, rough, and through could become Doh, ruff, and throo.
Wun uv the hardest things too lurn uhbout English is the pronunseeayshun.