Where do I invest first?

You've got your cash and the willingness to invest it for the future. Where do you start? First your 401(k), then a Roth IRA, next other taxable investments such as mutual funds or individual stocks.

Hierarchy of investment, according to Motley Fool

First, invest in your company's 401(k)
Take full advantage of the company match. (Beyond that, consider your other options.) What to invest: tax-inefficient investments such as corporate bonds and high-turnover stock funds. More on tax-efficient investments.

Next, invest in a Roth IRA
Use this account for relatively tax-inefficient investments that you'll hold for a long, long time. What to invest: High-turnover stock funds and high-yield bond funds are options, as are real estate investment trusts (REITs), which can be thought of as high-yielding small-cap stocks. This also could be the account where you do your short-term trading of individual stocks, if you're into that kind of thing.

Also: “Since contributions to a Roth IRA are after-tax contributions, a person should convert this contribution to a before-tax contribution.” How: These after-tax savings rates can be converted to before tax savings rates. This is done by dividing such after tax savings by 1 minus the marginal income tax rate. Source: tiaa-cref

Once you've maxed out the previous options, you still might want to contribute to your plan at work to get the tax deduction and tax-deferred growth. But, your investment options will be limited.

Third, invest in taxable investments (such as plain ole stocks or mutual funds).
What to invest: Stocks that you buy and hold for a very long time — especially stocks that pay little to no dividends. You don't pay taxes on these investments until you sell, and then at the relatively lower long-term capital gains rate. Also, any bonds that pay interest with special tax treatment — such as Treasuries and municipal bonds (which are usually free of both state and federal taxes).