ok buying chips is really quite simple, you get what you pay for. You can buy 11.5 gram chips for $20 or $120, the difference is huge if you intend to use them a lot.
Cheaper sets contain small flaws, not a huge issue when you look at a single poker chip, but massive if you like to stack em up (hi john).!!! In this way the actual weight is not a major issue, anything over 9g is fine. Just remember a good poker set is for life and i wouldnt go for anything under $50, unless your a casual player.
Not shipping to the US at the moment either folks sorry.