It's time to ditch those college sweatshirts for a professional wardrobe.

Dressing like a grownup doesn't have to be overwhelming or expensive. Even if you're on a budget, you could end up on your office's best-dressed list.

Step 1: Take inventory of your closet

Before hitting the stores, take stock of your wardrobe. This way, you won't accidentally buy anything too similar to what you already own.

"Think of it as doing inventory," explains Allie Brandwein, a wardrobe and style consultant. "This isn't something a lot of 20-somethings think they need to do but they should."

Brandwein recommends combing through your wardrobe every six months. You might be surprised by what's hiding in your drawers and not need to buy too many outfits.

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"I think a lot of people have a lot more than they think," adds personal stylist and fashion consultant Sarah Perpich of StylishSarah.

Step 2: Make a shopping list

Once you know what's in your closet, it's time to determine what you're missing.

Maybe you already own a great pair of slacks but could use a few button down shirts or sheath dresses. If you're not sure what you should add to your collection, Brandwein recommends making a dream board on Pinterest or combing through online stores for ideas.

"Taking the time to do this actually gives a lot of people who don't have a fashion eye, a nice bird's-eye view of the literal pieces they'll need," she explains.

When crafting your shopping list, focus on quality, not quantity, says Melissa Sotudeh, a certified financial planner at Halpern Financial.

"All you need is a couple of anchor pieces, like a basic tailored skirt, dress and trousers with a few white shirts and cardigans," Sotudeh recommends for young women.

For men, Brandwein recommends looking for a well-fitting sport coat or blazer, an oxford shirt, a pair of trousers, a pair of chinos, a short-sleeve button down and a slim pair of denim pants.

Step 3: Splurge on quality pieces

When trying on outfits, it can be tempting to buy anything that fits. But is that blazer worth the hefty price tag? Consider the cost per wear, says CFP Jonathan Swanburg of Tri-Star Group.

"A good belt or shoes that you wear everyday will have a much lower cost per wear than a good suit that you wear occasionally," Swanburg says. "Also, a pair of pants that will last 3 years will likely cost less in the long run than a cheaper pair of pants that will only last 6 months."

You might also consider spending money on timeless pieces rather than trendy ones.

"People will notice the suit with the unique cut or color if you wear it too often," Swanburg says. "A basic dark blue suit can be worn more frequently without raising any eyebrows."

Step 4: Explore the sales rack

After you've purchased the basics, try filling out your wardrobe with fun, seasonal pieces. The discount rack is a good place to start.

"Once you know which brands fit you well, figure out when their big sales are," says Jeana Salman, a CFP at Delta Community Credit Union.

You could also check out local consignment shops, says CFP Kristin Sullivan of Sullivan Financial Planning.

But don't get carried away.

"Good work wardrobes are acquired over time," says CFP Douglas Boneparth of Bone Fide Wealth. Taking a gradual approach will not only give your wallet a break, it'll "allow you to cultivate different looks and styles across the seasons."

Step 5: Take care of your clothes

It's important to maintain your professional wardrobe so you'll be able to wear the outfits for years to come.

If your new clothes aren't fitting perfectly, Brandwein recommends taking them to a tailor.

"Tailoring is so important. You can buy a cheap $30 shirt and have it hemmed and then it looks super polished, like an expensive shirt."

It can also help to carve out money in your budget for dry cleaning, as professional attire often requires special care, says Niv Persaud, a CFP at Transition Planning & Guidance.

To lengthen the time between dry cleaning trips, Salman recommends buying a steamer.

"For $30 or so, you can steam many of your clothes to save a small fortune on dry cleaning bills and look polished," she says.