Having $3,000 ready to invest opens up plenty of possibilities on the ASX.
For me, exchange-traded funds (ETFs) would be worth considering because they can put that money to work across a large number of businesses straight away.
These three Vanguard ETFs would all be on my shortlist.

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Vanguard Diversified High Growth Index ETF (ASX: VDHG)
For someone wanting to keep things simple, the VDHG ETF could be a strong option.
The fund is effectively a ready-made investment portfolio. Around 90% is allocated to growth assets such as Australian and international shares, with the remainder invested in defensive assets such as bonds.
That gives investors exposure to thousands of securities across numerous markets without having to decide how much money to allocate to each one.
Vanguard also takes care of rebalancing the portfolio over time.
I think that makes the Vanguard Diversified High Growth Index ETF particularly interesting for an investor who wants to buy one ETF, keep adding to it, and largely leave the portfolio management to Vanguard.
Vanguard Global Technology Index ETF (ASX: VTEK)
Investors looking for stronger growth exposure might prefer the VTEK ETF.
This fund invests in hundreds of technology stocks from developed and emerging markets.
Its holdings include businesses such as Nvidia, Apple, Microsoft, Taiwan Semiconductor Manufacturing Company, and ASML Holding.
That gives investors exposure to several areas I expect to keep attracting significant investment over the coming decade, including artificial intelligence, semiconductors, cloud computing, and software.
Of course, concentrating in one sector would bring more risk than choosing a broadly diversified ETF.
But for someone comfortable with a higher level of volatility and looking for long-term growth, I think this Vanguard ETF is a top option.
Vanguard S&P 500 US Shares Index ETF (ASX: V500)
The V500 ETF is another Vanguard fund that I would buy.
It tracks the S&P 500 Index, providing exposure to around 500 of the largest companies listed in the United States.
That includes technology businesses, but also major companies across healthcare, financial services, consumer products, industrials, and many other industries.
I like this because investors can participate in the growth of corporate America without relying on a handful of individual stock picks.
The ETF also has a low management fee, which can become increasingly valuable over a long holding period.
For someone wanting to put money behind US shares, I think the Vanguard S&P 500 US Shares Index ETF could make a lot of sense.
Foolish takeaway
I think all three Vanguard ETFs offer something worth considering for a long-term investor.
Which one I chose would depend on what I already owned and where I wanted more exposure.
With $3,000 available, I would be comfortable putting the money into one of these ETFs or spreading it across more than one. The important thing for me would be choosing the opportunity that best complemented the rest of my investments.