What?! I thought there were no rules in fashion! Generally speaking sure! I have just a few rules I live by though.
Shoes: Each season (there are only 2 seasons where I'm from, Summer and Sorta Winter) I get flats or sandals in the following colors: white, nude, black, dark brown, light brown, gold, and silver. Those are my mainstays. The more expensive they are, up to a point, the longer they last. I can use some for a few years until they bite the dust, then I just replace that specific color. However, I always have those color combos in my closet at all times. Obviously I buy other types and colors, but that's my general rotation.
Purses: Ugh, me and purses have a tumultuous relationship. Same goes for these though, I generally don't buy colors other than neutrals. Why spend a huge amount on a purse I can only wear occasionally? I also invest in my purses, the more expensive ones just last longer. So while I'm over here with my $$$$ purse for years, you may be purchasing purse after purse...and in the end you spent just as much as I did...on multiple purses...that fell apart. So think about that next time you go to buy a purse!
Jewelry: Guess what? Same goes for jewelry. I tend to buy real gold, real silver, and real gemstones. Investment pieces that I will have forever and be able to pass down through my family. I do get hooked on fashion jewelry though, but surprise surprise, the more expensive stuff doesn't turn your neck or finger green and lasts longer. My mainstays are the following: Gold ball studs, silver ball studs, diamond studs, a two tone watch (so it matches everything), Gold hoops, Silver Hoops. You get the picture. Whatever I buy, I buy it in silver and real gold. So I can wear it with whatever. In most of my pictures you will see me with just a thin gold band on my finger. Yes, I have a diamond engagement ring, I just never wear it. I'm just not a flashy ring girl, never have been. I bet the husband would have appreciated knowing that ahead of time, ha! My rings are two tone as well though. I have two thin gold bands, and a platinum engagement ring to go in the middle of those. So it will all match whatever I want it to.
Nails: I have a lot of favorite nail polishes and such. If you have known me for a long time though, you should know my nail routine. For over a decade I have done pretty much the same thing. In summer my toes and fingers are pink, and when it gets colder I change my toes and fingers to red. I change up my finger nails occasionally, but my toes will always be red in winter and pink in summer.