Ive done workin this field.

if u must use extension cords, u should use the expensive ones AWG12 or even AWG10 if ur running big loads.
u will find this rating on the cord itself and the package when u buy the ones u really need
each main cord should go to a separate circuit in the house,
take the time to identify breakers with as little useage as possible.
u should always try to stay at 75% useage on a breaker.
add up the appliances amps ratings on a circuit.
for a 20 amp breaker, try to stay no higher than 15 amps of useage.

do u follow so far?