First of all, bodybuilding or the new Physique category is something that takes YEARS of training and eating to accomplish. It definitely requires heavy lifting to build up what you need for the category...You're not going to decide you wanna compete one year and actually compete that year LOL!
The training is probably THE most important thing for bodybuilding or physique - you sort of have to enjoy lifting!!!
Figure and bikini are situations where young gals who are already in pretty good shape can build muscle for a year or two and then diet properly and show up nicely. Maybe they've been running for a couple of years and they add a little bit of weights to that....
Bodybuilding especially but also probably the new Physique thing are situations generally for women who are a little older than the bikini girls and maybe? older than the figure girls. They require several years of heavy lifting and semi-proper eating before there is enough muscle to even be there to be appropriate to the category.
So, briefly, the diet for the first three or four years, which are just training (heavy and I mean the basic lifts like squats, deadlifts, bench, rows etc. as well as curls, tricep work etc.) is enough protein, carbs, and nutrients (veggies, vitamins) so you can build muscle without having your waistline go much over 30 inches (for a female). I'm a fan of ethnic food that isn't vegetarian. So, anything from chicken shawarma to curry chicken to chicken tacos to beef fajitas will fill the bill!!
You can have cheat type stuff but just stay away from the really bad cr*p like soda, twinkies, you know that sort of thing. Make sure the meals have something nutritious there even if you're broke and it's just rice and beans....
And, of course oatmeal, whey protein, bananas and snacks like that too!! When you are in "off-season" and trying to increase your lifts, you do have to eat consistently so they'll go up.
It also depends whether you start out at an appropriate weight for height or if you start out a little overweight or how? If you start out overweight, you will want to watch the food more carefully than if you start out weighing less than you want to weigh.
Supplements for off-season gals who want to do physique or BB in a couple of years I would say just the basics like a good multivitamin, whey, and some BCAA's.
As far as the contest diet, generally the competitors do that with the help of a coach for the 12 or so weeks before the contest....that part is more similar to what the figure girls do.
It's the offseason eating that is more, um, munchier for girls who lift heavier and may want to do the physique sort of stuff.
Well, I hope I helped.....what is the year you maybe want to compete??