OK, guys, I've solved the problem with this characters as well.
So for those of you who still have the problem like me, I'll try to explain what I've done.
First problem was I didn't have my native language at all, although I've downloaded language pack from virtueMart and copy paste it on my computer(I'm still working local) in the joomla virtueMart folder(components\com_virtuemart).
But the problem was, there was no croatian language in folder administrator\components\com_virtuemart\languages.
When copy/paste language pack there as well, I've got cro.lan. but I got problem with characters ČĆŠŽĐ.
Since nobody could help me here, I've started to search, and I've found out that in every mylanguage.php code starts as follows:
global $VM_LANG;
$langvars = array (
'CHARSET' => 'ISO-8859-1',
and that was a first problem.
If you change 'ISO-8859-1' to 'UTF-8' in every single php page in folder languages you'll get what you want. But croatian language files are not correct, and missing some translations.
So for Croatian this is the link where you can find croatian language pack that is ok:
http://www.crojoomla.com/component/option,com_docman/task,cat_view/gid,94/Itemid,28/Hope I helped somebody!