Hoo boy, that is really the hard way to fly.

Most highstarts will put a glider up at least a couple of hundred feet. And it's not unusual to fly a couple of hours off a highstart and never find a thermal. Finding thermals is directly related to how far you can search for them which is directly related to how high you start the search. So when you start the search from a throw, you're really limiting the search.

I would suggest that what you really need to do is to find an area large enough to setup your highstart. The only successful gliders that have a hope of finding lift from a throw are the discus launched ones.

Are there no glider clubs around you? They would have a suitable site and would be glad to have you as a guest. And would help greatly to learn the sport.