If the only dividends and capital gains are those reported on Form 1099-DIV, the online Free Edition is probably be sufficient. Online Premier would be needed if there are capital gains or losses other than those reported on Form 1099-DIV.
You can start with a lower version of online TurboTax and TurboTax will prompt you to upgrade if your tax return requires a higher version.
Some people may qualify for the Free File Program (formerly Freedom Edition) regardless of the complexity of the tax return: https://turbotax.intuit.com/taxfreedom/
