[Zeke]

It's not as simple as combining "hots" but it isn't that difficult. You need to know what you are combining. You mentioned a few individual circuits in the basement. IDK what's in the basement but lights should be separate. And you can put a lot of lights on one 15 amp circuit, like 20.

You should know the load is though. All LED's are going to be a smaller draw. The point is, if you have a resistant heater in a bath, that's one circuit. If you have receptacles in the bath and there will be hair dryers, curler warmers, a towel warmer and a milkhouse heater, obviously more juice is needed.

Most wall recep's are in groups of up to 15 or so on one circuit, but you wouldn't and can't do that in the kitchen. So if you have a huge entertainment center, don't be hooking up a couple of power strips to a dozen devices. Put some recep's in that wall with a couple circuits dedicated to that. BTW, it's a good idea to run a 'clean' ground to those that doesn't combine with others; a home run for the ground, neutral and hot and you will hear less electrical noise on your gear.

Many recep's in your house, like the one required for a hallway more than 10' long will be used for a vacuum cleaner and that's it. Many others will only see occasional use. It's good to know those and not waste circuits not needed.