Silicon molds can be very handy, one thing I have found however, is the multi-colored ones are very difficult to achieve in reality.
By that I mean the ones with sections of the mold in different colors, like they might have a face or details in one color, then other colors for different bits. sometimes they show example finished product that has 5 different color fondant/gum paste areas on the one thing. Those tiny little bits are very hard to judge right and put the right amount in. You could try using one color and painting the details, but that takes a lot of skill also.
For single color stuff, like a ribbon bow or similar they are great however. Or if the color change areas are large enough, no problems.
ABe careful about size before you buy. I have bought some and they are tiny moulds. Best silicone moulds I have bought for fondant are from Neitmoulds.com really excellent, good sizes and excellent selection. Remember if your are using fondant add sprinkle of CMC to help dry it out.
Moulds can be great, especially for cupcake toppers but, as mentioned above, check the size as a lot of them are small. Karen Davies has quite a selection on her site but I mainly mention this because she also has tutorials on coloring the fondant after it is moulded. Flexible silicone is the easiest to use. I have quite a few that I bought on ebay from China.
You can always make your own also, which is so much cheaper. Hobby Lobby has the stuff and you can use a 40% off coupon, my set will make about 100-1-1/2" diameter molds, or less if the piece is larger. I think I paid $12 for the set, and it is food safe.
The jewelry section and miniature doill house section is always a good place to check, and if you visit etsy, do a search on cabachons (I think this is the correct spelling of it) they are the plastic looking flowers that you can also use for molding. A HUGE selection to choose from, and there are some that are 3" across.
Just FYI
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