Welcome to the forum! 10 gold barbs should be fine in a 30g. They seem to be pretty adaptable for water hardness and pH, so unless your water is freakishly soft or hard, no worries there.
What kind of labeo are you thinking? I agree that red tail black sharks would be a bad idea in a 30g. They tend to get very aggressive as they age, and two in a 30g would probably end up killing each other and terrorizing the gold barbs. They tend to like it warmer than gold barbs, too.
Make sure you know about cycling before you add fish.