You should call an electrician when lights flicker or outlets are working intermittently, or when breakers are tripping.
You would need a new circuit ran if you are using more power than is available, possibly tripping the breaker.
If your circuit keeps tripping something has gone wrong, too much power is being used, breaker or outlet could be bad or a loose wire.
Yes, I install ceiling fans!
Yes a dimmer switch can be installed where a regular switch is currently.
If you plug something in to an outlet and it is loose or falls out your outlet needs to be replaced.
Lights can flicker for many reasons, it could be the light fixture or a loose wire in your light.
To save money on electrical bills change your light bulbs to LED light bulbs.