Boogaloo (like your nickname here
),
Don't feel bad. You are not alone. It's never too late to start saving. Be glad that you are in a position to do so -- unlike many other Americans, who have yet "to get it."
You're 48 so, so you have some 18 years or slightly more to still save if you want to work until full legal retirement age (assuming that SS is still around). Don't plan on SS, if it is available, than fine, but don't plan on it and save all you can.
The only advice I can offer here is yes, you really do want to concentrate on the "big 3" -- they have the least costing management fees of anyone else out there.
And the only second bit of advice is to stay away from annuities and insurance firms (for investments) -- in most cases they are not worth it. Read everything you get, never trust what anyone says about an investment; read the contract, prospectus, anything you can get your hands on.
Buying and renting housing to other people here in California may be an option if you are a handy-man and wish to remain in this state after retirement. And if you have the patience for dealing with people not always under the best of circumstances (ie collecting rent, fixing, evicting -- in some cases -- etc.). Neither me nor my DH would be able to do that.