I'm a 24 year old Canadian man on an extended holiday abroad. Most people I meet are from the United Kingdom, Germany, and Ireland. The country where I am is irrelevant because I rarely meet people from it in my hostels.
Due to a fundamentalist religious upbringing (which I have now abandoned) and a mild case of Asperger syndrome (which I can usually conceal and does not affect me day-to-day) I made no serious efforts to date until early 2018. I'm pretty clueless about the whole thing, but I've been reading up and making serious self-improvement efforts. It's led to some successes, but I still haven't ever kissed or had sex.
My dating strategy in the hostels I stay at has been to have a few conversations with a girl, and if she seems reasonably friendly then ask her out to coffee. This hasn't worked yet. The first time I tried it, she told me "I don't date people from the hostel", then just a few days later started a casual, summer-lover relationship with a different guy there. When I confronted her about this she said that in reality she had rejected me because "you're looking for love". Something almost identical happened two days ago: she rejected me because she wants to be a free spirit, but when I asked her if she'd sleep with someone at the hostel she said "yes, if we had a connection".
My friend back home has told me "in hostels and girls travelling—they aren't planning for it to be a long-term marriage and sometimes the sex is just sex". Great, now how do I start something that isn't a long-term marriage? To be clear, I'm open to short-term dating. In my position I'll take anything.
TL;DR I want to date girls from my hostels. I would prefer something serious but I'm open to something casual. When I ask them out in the way I currently do, they say no thinking I want something serious. How do I start something casual?
This is not a duplicate of this question. While it does contain some useful advice, I have the exact opposite problem: I would prefer a serious relationship, but the women I meet don't want one. Plus I'd like to know about the process of establishing a casual partnership in more detail.