Depending on your income and tax brackets (before and estimated in retirement) you could do either traditional or Roth IRAs. The sticking point on these is that you can each only contribute $5,500 - so 11,000 a year for the both of you (in your own accounts), so you would have to run the numbers to see if the tax deferred (traditional) or after tax (Roth) would be the best bet for you.
Then a regular taxable account if you have extra money to get it growing. It should be possible to save and invest and still retire early without a 401k or other work retirement account, but the earlier you start the better.