Complete chip sets should be purchased with a few things in mind: How many chips do you need? How much can you afford to pay for your chipset and how many players will be using the chips in a game. As with most things, you pay for quality and the best advice is to buy the highest quality you can afford. It is rare to be sorry that you opted for a higher line of goods so buy the best your budget allows.
A good rule of thumb for quantity follows:
3-4 Players 300 chipset is usually enough
4-6 Players 400-500 chipset will suffice
6-8 Players 500-650 chipset is required
8-10+ Players 1000+ chips depending on numbers