Camilo is correct that there are a lot more people wanting to learn English.  But there is a caveat.

I offer to help people all the time and they have my Skype ID.  If they speak a language that I currently speak then I do this for free to practice my language skills.  Also, explaining English concepts in Spanish or Chinese for example enhances my own skill.

I'd say maybe 5% of these people actually truly want to practice.  Most of the time they are time-wasters who say they want to work on their English but they just send you messages in their native language asking what you did over the weekend or what you like to eat.

They're not serious about learning a language, they are just bored and want to talk to someone.

My best advice is to find someone who wants to learn your language and you should be proactive.  If they agree to help you, try to offer something in return like helping them learn your language etc.  If you're not paying with money, you need to try and offer something.

I don't think there is a best way. The number of English learners outnumber ny far the number of English speakers learning foreign languages and truth be told most of them don't find it something serious. Also, I guess there are not many people interested in learning Sinhala.

The problem I have is I get a million Indians and Chinese who just want to chat and speak in English for social reasons - when they have no problems in English at all - or with a slight Chinese accent.

The other problem is the languages I'm learning, or have learnt is that there is no resources for those languages. So there is no real sharing or exchange of languages - such speaking / chatting in English.

So usually I just ignore most requests. I agree its hard for the 5% of people who have problems with English and iTalki would be a benefit.

Having said that, I would give you a feasible option that is to choose some people who have equivalent English proficiency to practice and not necessarily a native speaker.

I find it really difficult too. I've written to some people suggesting the idea of helping each other with languages and no one has replied. Since I created an account here I have spoken with nobody and it's a little bit disapointing. I consider many people want to learn Spanish or English but I don't know why I haven't found somebody to talk with.