3 steps a 27-year-old millennial took to build a $250,000 investing portfolio

• 27-year-old Shelby Farnsworth built a $250,000 investing portfolio using several strategies.
• She automated her savings to put away more, and cut back on her housing expenses.
• She also took advantage of her employer's 401(k) program early on, and got a match.

Shelby Farnsworth, a 27-year-old global supply manager at Lyft, started saving and investing as soon as she could, and it's helped her build a large investment portfolio at a young age.

Farnsworth used simple accounts almost anyone can open, and was able to save and invest her way to a $250,000 portfolio in about 10 years.

Here are the three main methods she used to reach this major milestone quickly.

She automated her investments

From her 401(k) to her individual investing account, she automates her finances to make it easier to save and invest.

"Living in California, it's hard just because everything here is expensive and there's always something going on. So for me, it's having everything on automatic withdrawal," she told Insider.

She sets up automatic deposits from her checking account to other saving and investing accounts.

"Between my 401(k), I never see that money. I've got money that's set up to go to the Roth IRA, and then money set up to go to my personal management fund," she said.

Automating her investments made it easier to save consistently and save more over time.

She tried to keep her housing expenses as low as possible

Living in San Francisco, Farnsworth's largest expense has long been her rent. But over the years, she's found ways to get creative to keep her costs down.

"A lot of it was making sure that my rent was controlled," she said. "I lived in some pretty interesting living situations just to make sure that that huge chunk of change where people typically spend 50% or 60% of their money, mine was at 20% to 30%."

As her income has risen, she's been able to move into a one-bedroom apartment - no more roommates or "interesting" situations - but her housing costs are still 30% of her income.

She started investing as soon as she could, and took advantage of employer matches

Since she started working, Farnsworth has been taking advantage of 401(k) programs offered by her employers. By starting to invest as soon as she could, she's been able to use the power of compound interest - where money grows based on money earned - to her advantage.

"Just having time on my side through college and my very early 20s, that small chunk of change has become larger and larger and larger as my salary has grown," she said.

Her employer match has been another critical part of the equation - that match equates to free money her employer contributes towards her retirement savings, up to a percentage of her salary. Matches are an easy way to save more, without having to contribute more. It's something that helped Farnsworth grow her portfolio and build her net worth.

• Read more from Master Your Money:
• A millennial couple explains how they use automatic savings and bill pay to avoid money stress in their relationship
• A woman who married into 6-figure debt shares the strategies she and her husband have used to pay off $50,000 so far
• A 35-year-old US Navy sailor who used military perks to 'house-hack' his way to passive income explains his strategy
• A Phoenix family's year-long savings sprint helped them save $24,000 to buy their first home and provide a launching pad for their second