This is indeed a dilemma, but one that can be easily solved! You have overcome the biggest hurdle of all - by recognizing that you have slipped into a style slump and being willing to climb out of it.
First of all, style is more than just a wardrobe. Style is a talent (and, luckily, one that can be acquired)! A plain little black dress can be transformed into a chic fashion statement by the perfect shoes, wrap, handbag and jewelry. And it doesn't need to put you in the poorhouse either!
I would suggest starting with a few great quality basics, then build from there. The framework of your wardrobe should always be the best quality that you can afford. Top quality basics will last for years, will never go out of style and will be a great investment.
Start with a fitted blazer. A classic neutral like brown, navy or charcoal can coordinate with just about anything. A blazer always adds an element of style and can be worn with jeans, trousers, skirts and even dresses. Choose a fit that flatters your personal body type and make sure it is very good quality fabric, cut and style. Don't scrimp here!
White button-down blouse. Another classic. Can be worn with the blazer and jeans for a great casual weekend look or paired with a skirt and heels for an easy business lunch.
Cashmere sweater. Nothing feels as exquisite as cashmere! I would opt for a great fitted cardigan because of its versatility as well as style. It can be worn over blouses, under jackets, with jeans, trousers, skirts and dresses! As I said, very versatile!
Fabulous denim jeans. Another no-scrimp item. Take an afternoon (and a very good friend who will be totally honest with you) and try on every pair of designer jeans in Saks, Bloomies or Nordstrom till you find the pair that is most flattering to you. Hint: Straight leg styles are universally the most flattering, but a slight boot-cut will usually work too. Now that you know which jeans looks best on you, scour the sales and keep an eye on great online sources for good deals and you'll never be without a great pair of jeans!
Wool trousers. One great pair of fantastic trousers in a not-too-wide-leg style, (but not skinny or flared either.) Think timeless style. Black, navy or khaki.
A-line skirt. The classic style. Always looks good, always flattering. Keep it about knee length or just above (too long and it looks frumpy, too short and it looks trashy). I love skirts because they can be dressed up or down, depending on the look you are going for. I love to wear a classic a-line with a great tee shirt, a denim jacket and a pair of wedges. Or, you can go glam with a shimmery top, elegant coat and classic pumps.
LBD. Every girl must have a great little black dress! Here, again, go with what flatters your figure the most. If you have a great waist, emphasize it in a chic wrap dress. If you have sexy arms, go with a halter-style or a sleeveless dress.
Now that you have the basics, you can bump up the volume with tops, tees and other separates, and you can add individual style with accessories. A great tote bag for work. A chic little shoulder bag for evenings. A classic pair of knee boots. A pair of basic black pumps. A pair of chic neutral flats. A pair of mid-heel t-straps or Mary Janes. A pair of sexy, sassy skyscrapers to wear with the LBD!