I've made wedding dresses for friends and helped other friends make theirs. If you have some sewing experience and pick an easy or intermediate design, you can successfully sew your own dress.
First, consider the cost. Weddings are big business in the US, and dress vendors cater to all budgets. Fabric, especially luxurious special occasion fabrics, can be costly. Making your own might actually cost more than a similar ready to wear dress!
Second, compare your skill set and dream design. I do not recommend beginners tackle a project like this. Intermediate sewists should stick to simple designs or patterns labeled "easy". Special occasion fabrics can be challenging, and can turn an "easy" project into "difficult" very quickly.
Third, consider the time element. Estimate how long it will take you, then double that for a more realistic number. This is why I chose to have my dress made for me, even tho it was well within my skill set. I did not want to spend precious days before my wedding making a sea of wire ruffles
If you decide to take the plunge, allow yourself plenty of time and pick patterns in your skill set.
Get a book (like Sew a Beautiful Wedding) or take a class in making special occasion wear, there are some simple techniques that make the difference between homemade and couture.
Make a sample garment from your chosen fabrics. It doesn't have to be big, fancy or white. For example if you've picked a white satin, get some in a different color and make a simple shell top or straight skirt to understand how the fabric will act when you are making the dress.
Make a mock up. If you don't want to waste money on "test" fabric, use old bedsheets or choose a fabric that will make a wearable garment. I like to use cotton prints for this step, because the end result does not scream "wedding dress mock up", and when shortened to knee length, they often turn into nice tea dresses.
After tweaking the mock up for fit, transfer ALL the changes to your pattern pieces (or, if you've used old sheets, just disassemble the dress and use the pieces as your pattern pieces)
And remember to allow yourself plenty of time!