Portable mic booths are less effective than most think, you'd be better off putting a a few squares of acoustic foam on each wall of the target room.
Thick carpet / rugs, material curtains instead of blinds, hanging up clothes / blankets can make a big difference. Some of that is a bit more on the ghetto side of things but it works, most effective thing would still be putting up a dozen pieces of acoustic foam. Post production can help significantly too, but only if the raw audio is manageable. Basically if you've got echo you're stuck with the raw audio, applying effects on top of that may just make it worse.
But if you can get the raw audio to sound decent via acoustic treatment, applying a bit of noise reduction, EQ, and compression can take your quality to the next level.