making your own bodice?

"Bodice" is a very loose term. A real supportive garment - with strong boning, that shapes your body - is probably not worth the difficulty level if you've never really done work on that level before. If you do a lot of sewing normally, then maybe the difficulty jump is alright; you'll probably just need a little bit of help (especially with fitting/measuring; it's pretty much impossible to measure yourself for something that needs to fit so precisely). If you don't sew much (or at all), I wouldn't attempt it for a first project.

However, if you're just looking for a ren-style bodice that's there to look nice but does not need to shape your body - essentially a tightly-laced vest with *maybe* some plastic boning in the front - they're really not that difficult, and there are a number of commercial patterns available. /tangent rant In fact, you can see many vendors at ren faires selling bodices that are clearly Simplicity #5582, can't a fantasy-themed store have a little more creativity, if only with the trim? GRRR. /rant Actually, Simplicity #5582 is not a bad place to start; I do not believe it has any boning in it and would probably be a good pattern for a novice seamstress, so that you learn how the different shapes lay on your body. Just dressing up the fabric or trim can go a long way in making something that looks unique, and that's something that's limited more by budget than skill level.