Belegarth caters to people who are more into the combat aspect of the sport. There's another group called Amtgard in North America that does more roleplay, questing, magic, etc but is similar.
In Lithuania you might have a harder time finding a group like this. In Germany there's a large annual event called Drachenfest that is one of the largest LARP events in the world. There's also various chapters of the SCA (Society for Creative Anachronism) which is quite popular accross Europe although they're more historical and less fantasy-based. Might be worth checking them out. Good luck!
How expensive is it? I assume props cost a lot.
That's a tricky question.
It's free to participate and most groups have gear you can borrow for your first few months.
Eventually you'll be expected to get your own gear. You can buy a decent professionally made one-handed weapon for $25-$40 - check out some gear here
https://www.forgedfoam.com/?product_cat=full_contact
Some people make their own gear, which significantly reduces costs. A home made one handed weapon might run $10-$20.
Of course just like any other sport you can spend as much as you want, and get really fancy gear if you want to. Some people get super-lightweight weapons or commission hand-made plasti-dipped artisan shields that are like works of art and those can cost hundreds. Check these out:
https://shield-shop.com