If you are thinking about collecting casino chips as an investment, you really should think twice about doing so. There are several other ways to better invest your money, than to put it into casino chips.
You should look at collecting casino chips as strictly a hobby. Sure, you want to get the best deal possible when buying a chip. And if you have to sell that same chip down the road, you would like to make a profit. When it comes down to it though, unless you have a one of a kind, highly sought after chip, most common chips will not go up that high compared to other investments. And those one of a kind rare chips are VERY few and far between.
Collect casino chips because you enjoy doing so. If you happen to make a profit down the road then so much the better. The real profit will be in the enjoyment you had over the years, collecting the chips to begin with, and the many friendships developed over the years with other collectors who have similar interests.