A mix of growth ETFs with the stability of the market's gains can help you achieve your long-term investing goals.There are multiple strategies for investing, and no one-size-fits-all approach. While some investors prefer to choose individual stocks to create a diversified portfolio, some leave the selection process to index funds they buy, and many opt for a combination of both.If you're in one of the latter two camps, choosing an array of exchange-traded funds (ETFs) can help you achieve millionaire statu ...