Originally Posted by cvision

First of all, if you want complimentary lounge access on domestic itineraries, you have to go for any non-US airline's frequent flyer program. I think neither DL, UA or AA (as for AA I know for sure) have such access for their mid-tiers and greater.
This means no access to United Clubs / Admirals Clubs if you're flying domestic (although you could get that with their CCs I think).

Second, for lounge access via status you need at least(!) the second highest tier, which is Sapphire for oneworld, and Star Gold for Star Alliance.
I'm a bit in a hurry right now, but if I find time later, I'll elaborate more if someone else hasn't already.

But specify: What is your travel pattern? Airline pattern? Etc. pp.