I am wiring a basement and have plenty of spaces left on my 200 Amp GE panel for expansion. Should I use 14/2 romex for lighting circuits and 12/2 romex for outlets and appliances. How many lights typically on a 15 Amp 14/2 circuit (standard 2 bulb ceiling lights) ? How many outlets can be daisy chained on a 20 Amp 12/2 circuit ? Should I just use 12/2 all around? And last any appliances beside a electric range that should have their own dedicated circuit normally?

A 20 amp circuit can handle 2400 watts, and a 15 amp circuit can handle 1800 watts. If the loads will run three hours or more, the load applied must be derated by 80%, leaving 1920 watts for a 20 amp and 1440 watts for a 15 amp circuit.

Since electricians usually do not know what loads will be running how long, most apply the 80% derating for everything, leaves a reasonable safety cushion.

A lighting circuit needs to be able to handle all the lighting that will be on at one time. And since it is very possible to have a room's lighting on for 3 hours or more, we will use 1440 watts for the 15 amp circuit, and 1920 for the 20 amp.

Typical lamp wattage is a 60 watt, so a 15 amp circuit can handle 24 lamps(light bulbs), and a 20 amp circuit can handle 32 lamps.

I would use #12 wire and 20 amp circuits for both lighting and outlet circuits.

For residential there is no limit to the amount of outlets on a circuit, however the limit for anything other than residential is 180 watts allowance per outlet, so 10 outlets are the max on a 20 amp circuit, and 8 on a 15. These limits are widely used in residential as a guide.

As far as appliances on their own circuit, should be refrigerator, freezer, dishwasher, cooking appliances, air conditioners, humidifiers, heaters, etc.

When you say 10 outlets max on a 20 Amp circuit is that 10 double plug outlets or is it 10 individual plug outlets (5 double plug outlets). Would 14-2 romex and 15 Amp breakers be OK for a circuit that has 3 ceiling lights (2 bulbs each) with 3 on off switches. I know the recommendation is 12-2 with 20 A but this work was already done.

I mean 10 duplex receptacles. And the #14 and 15 amp breakeris fine with what you have for load.