It may sound hyperbolic, but you could build a million-dollar portfolio with just a few investments if you are patient and persistent.

When I say patient, I mean like 20 or 25 years of patience. And when I say persistent, I mean regularly contributing money to those investments.

And rather than racking your brain doing deep analysis and research to find the right stocks and then wondering if they are the right choices through bouts of short-term volatility, you can do it pretty simply and cleanly with a few exchange-traded funds (ETFs).

The beauty of ETFs is that they trade like stocks, yet they are diversified baskets of dozens, hundreds, or even thousands of stocks. So if the markets do get volatile, a good ETF can reduce that risk through diversification, whereas a portfolio of just a few individual stocks is more exposed to wild swings.

So, you could actually be well diversified with just three ETFs and have the long-term alpha to build a million-dollar portfolio over time. Those three ETFs are the Invesco QQQ Trust (QQQ +1.40%), the Vanguard Information Technology ETF (VGT +1.35%), and the iShares Russell 1000 (IWB +0.38%).

1. Invesco QQQ Trust

The Invesco QQQ invests in the stocks in the Nasdaq-100 -- the 100 largest non-financial sector stocks. It is synonymous with tech stocks, since they dominate the Nasdaq, but it is somewhat diversified, with 16% in consumer discretionary stocks, 6% in telecoms, 5% in healthcare, and 3% in industrials.

Currently, the top three stocks are Nvidia, Apple, and Microsoft.

QQQ Invesco QQQ Trust

The Invesco QQQ Trust has a stellar long-term track record, returning about 13% per year over the past 25 years, on average. So, if you invested $5,000 in the QQQ and averaged a 13% return over the next 25 years, contributing $100 to that investment every month, you would have about $304,000 today.

2. Vanguard Information Technology ETF

If you had another $5,000 to invest, another great ETF to buy and hold for the long term is the Vanguard Information Technology ETF. The technology sector has been the best-performing sector over the past 30 years, and it should continue to thrive as we move into the heart of the AI boom, which could last another 10 to 20 years. But beyond that, there will no doubt be another breakthrough technology, whether it's quantum computing, robotics, or something we haven't even heard of yet, to drive the market.

What's great about the VGT ETF is that it is one of the most diversified tech ETFs. It holds 318 technology stocks across all cap sizes, from megacaps to microcaps, and tracks the MSCI US Investable Market Information Technology 25/50 Index. So its top holdings are the same as the QQQ, but it has a far broader swatch of tech stocks, tapping into the growth potential of small- and mid-sized tech stocks.

VGT Vanguard Information Technology ETF

It was launched in 2004, so it has a 22-year track record. Over that time, it has averaged about a 15% annualized return. So, if you invested $5,000 and contributed $100 per month to the VGT, you would have about $437,000 across 25 years -- assuming it matches that 15% annual return.

3. iShares Russell 1000 ETF

If you had another $5,000, I'd suggest investing it in the iShares Russell 1000 ETF. I'd favor this over an S&P 500 (^GSPC +0.31%) ETF because it lets you tap into mid caps as well as large caps with the Russell 1000 ETF, giving you a bit more diversification.

And the iShares Russell 1000 ETF actually beats the State Street S&P 500 ETF (SPY +0.31%) over the past 25 years, with an average annualized return of 10.1% compared to 10% for the SPY.

IWB iShares Trust - iShares Russell 1000 ETF

So, if you did the same thing, a $5,000 investment contributing $100 per month, you'd accumulate about $177,000 over 25 years.

So add it up, and a $15,000 investment in these three ETFs would amount to roughly $918,000 in 25 years. The key is to have the patience to hold these ETFs for the long term and add to them consistently. Ultimately, you are paying yourself and investing in your future.

Investing in these three proven, diversified ETFs is a simple way to set your portfolio and forget it.