Pick up some staple pieces. Check out the trends for the season and look for some things to add to your closet that you're comfortable in. On trend pieces are bound to make you feel stylish and more comfortable!
Find your favorite colors. The more you love a color on you, the more confident you'll feel! It's not hard to figure out which colors look best; my favorite colors on me are plum and navy. I HATE the way blush and yellow look. Go by things like your hair and eye color and skin complexion. It isn't hard to look in the mirror and know if you like any given shade! Having a color palette that you can always go to when it comes to clothes is super helpful. Then for each season, clothes shopping is much easier - picking warmer colors in the fall and light/airy colors in the spring can all be from the same shades.
Find a couple of stores you know you love. Personally, I have a handful of "go-to stores" and a handful of stores I'll never shop in - everything else is in between. After a while, you begin to know which stores have the best pieces for you and which just aren't going to work no matter how many times you try. This makes it so much easier to shop online, and you also have a spot or two you can go when you're looking for something specific. I also like having my favorite store to boost my confidence if I end up trying a bunch of things on I hate. My favorites (size, quality and overall fit wise) are American Eagle, Old Navy, Rebecca Taylor and Banana Republic.
Take all of the pieces from your closet that you're uncomfortable in and put them away for a while. Maybe it's the holiday season and you've eaten too many cookies, or maybe you're going through a stressful time and put on a little weight. OR MAYBE you're on your period and are too bloated to care. Whatever it is, having it stare at you every time you open your closet doors is only making it worse! Put these pieces in a drawer or somewhere away until you're ready to re-evaluate.
Ask for some opinions on things you're unsure about. Whether it be your best friends, a cousin, sibling or your mom - plan a fun girls night in, play some music and drink some wine and try your "maybe" pieces on for them. Have everyone try on some things that they're on the fence about and give feedback to each other!
Wash your clothes in cold water and avoid thinking you gained 10 pounds overnight. It's always on the days that I feel zero confidence that my favorite t-shirt got thrown into the dryer, making it all tight when I put it on! I ALWAYS wash my shirts in cold water and hang dry them. Always. I don't care if it's a nice blouse or a pajama shirt - I like being comfortable and not worrying about my clothes shrinking makes everything so much better!
Stop dressing for other people! I think this is the most important point I or anyone could ever make! I WISH I could go back in time and smack some sense into my 7th-12th grade self, because I always thought it was so important to take note of what everyone else was wearing. If only I would have just worn what made me comfortable and what I liked most! Now, it's all about what I like on me and what makes me feel good. So important.
Keep it easy and effortless. Your personal style is about what you like and what makes you smile when you look in the mirror! It shouldn't be forced or even perfect. It's about yourself and your happiness!