I highly suggest the use of a flash with a loosering bit - keeps it way quieter in the mouth and allows for a better connection.
As far as for the bridle, about seven-ten years ago I splurged and bought two high quality, handmade dressage bridles. One is a snaffle and one is a double and they are of the same style (They are on my horse if you go to his page). Best thing I ever did, they both look new, haven't stretched or worn out at all (although my snaffle bridle could use an oiling..) and this is after nearly every day use, sometimes on multiple horses.
Now, I am one of those "buy it once" people. Some people like to buy cheaper stuff so they can have 3 bridles, depending on their mood, and one for a show. I like to keep everything the same and because I bought my bridles so high end and they are custom hand made I got them so they can fit almost everything I will probably ever own. They fit my 17hh, large headed Hano mare, they fit the smaller, funny headed schoolmaster I rode and they fit my current, arab faced horse as well.
Unfortunately the company I got them from has since disappeared (the bridle maker retired), but, you can find other gems in your area. Talk to your local dressage tack store to see what bridles they can get. Beyond that, I think your best resource is your local dressage tack store, they should have a wide selection in catalouges and will have in depth knowledge about quality, etc..
PS Stubben bridles are of excellent quality as well and can be less expensive then some "trendier" brands like Vespucci, Anky, Kieffer and Passier. I have one hanging around for tiny headed horses if I happen to be riding one.