Hi Brenda --
You have the most valuable coin from a Kiribati Millenium Set. It is valuable, worth about $238 US dollars.
The picture shown is not of your coin, but of one of its partners in a 5-coin set struck at 12:01 AM January 1, 2000 at the International Date Line. Kiribati, formerly the Gilbert Islands, became an independent nation in 1979 and soon discovered that collectors would pay good money for coins from out-of-the-way places. This is not uncommon for island nations.
Fluff and intrigue aside, your coin is worth its weight in platinum. I call (1) out-of-the-way places, (2) mint packaging, (3) fancy logos, (4) inspiring inscriptions, and (5) the dazzling look of proof coins 'fluff' because they do not add value to the coins. Be careful, though, shysters of various sorts will try to peddle these sets at prices far beyond what they are really worth. They are wonderful collectibles. But don't pay too much for them! You have to decide for yourself how much the 'fluff' is worth to you.
In summary, the coins in the Kiribati set are worth bullion value. That is, they are worth the value of the precious metal they contain. The $5 and $10 coins are struck in base metal, so they are not worth anything over a few US dollars. The $20 coin is struck in 21.4 grams (0.69 Troy ounces) of sterling silver. Sterling silver is 92.5 percent pure silver. Figuring an approximate current value of silver at $21 US dollars per troy ounce, the $20 Kiribati coin is worth 0.69 x 0.925 x $21, or about $13.
Use web sites such as kitco.com to look up current values of precious metals.
The Kiribati $50 coin contains 0.2 ounces of gold, and your $100 coin contains 0.2 ounces of platinum. Using calculations like we did for silver, the $50 and $100 Kiribati coins are worth $262 and $300 respectively.
More information about Kiribati coins can be found at this CoinQuest link.