Could someone recommend the best bang for the buck lav system for the 300-400 price range? Its to accompany my camera kit, so it'll be for simple interviews & such.

By lav system I assume you mean a wireless system. Search B&H's online catalog (bhphotovideo.com) for:
"sennheiser wireless"
"audio technica wireless"
"samson wireless"

Audio Technica's Pro 88W series is a good performer for $170. It's VHF system so it is more prone to RF interference.

Sennheiser's G2 system is extremely poplular at $499. I love mine. AT has offerings in that range too. Samson has some models in your range, but the pros favor Sennheiser, AT and the much more expensive Lectrosonics.

Thanks, the G2 system looks pretty nice. Looks like Ill have to save up a little bit more money for it.

I think I saw one of those audio technicas laying around my uncles house, maybe Ill borrow it until I afford the G2.

I have the Audio-Technica U100 wireless lav and like it a lot. It's worked flawlessly for me since I got it in March.