Trying to think this through.

I've currently not got enough power in my basement garage/shop. Pop breakers constantly with the 15A circuits.

In my basement I have a 200A Square D panel box that is completely full.

I'm thinking of adding a 100amp Square D sub panel box next to it.
It's in a finished den with no insulation in the walls. I'm gonna tear out the drywall and do all this while everything is exposed.
I'm planning on moving all basement circuits from the 200A panel to the 100A panel to allow room for the new panel circuit.

I'm planning on two 30A circuits from the sub panel to the shop. One will be a 220v and one a 110v.
I also plan on running at least one 15A or 20A circuit to the shop, just to have the extra power.
I also plan on running at least one 15A or 20A circuit to the shop, just to have the extra power.

What else do you suggest? I don't want to revisit this project because I've not thought of something important.

Don’t have enough power or don’t have enough circuits? You have gas heat? Sounds like you need a 60a MLO sub panel.

Don't have the power I need on existing circuits. No room on existing panel to expand.

That first question Dixie asked is the important one to answer. If you could simply upgrade to a larger load center then that may save you some labor. How many circuits does the existing load center have?

Why don't you just get a bigger panel?

Don't quit your dentist job.

Just remember to use the appropriate wire for the 15A (14-2) and the 20A (12-2) circuits.

And in the sub panel (Unlike the main panel) the neutral and ground bus bars must be kept separate.

Irish Guy hit the nail on the head.

I had to do the same thing last year for the very same reason. Added in 100A Sub and all is well. Biggest PIA is the heavy gauge wire running from your 200 to your 100A Sub. It's like trying to bend and maneuver re-bar.

Plenty of you-tube videos that will show you how to do it properly and up to code.

Sounds like you need to hire an electrician.

square d makes what is called a piggy back breaker. 2 breakers that is the same size as 1 regular breaker. IF you really want to waste money on another panel you will need a 100 amp lug only panel. Install a 100 amp breaker in the existing panel and run #1 or #2 copper wire to the new panel. That will leave you with 2 circuits in the old panel that would have to be rerouted to the new panel. Cheapest way is to go buy yourself a few piggyback breakers.

Piggybacks don’t work in every panel and depending on what’s where in the existing panel may or may not work out. A 60a sub panel next to the one he has ain’t gonna be much more and be a lot neater and versatile for adding stuff later. If Fatty was closer I hace a 12 circuit panel and some homeline breakers I would give him.

This box is already half full of these. I'm going to have to move some of these over to the new sub panel in order to make room in the main panel to even run a sub panel.

I wouldn't run any 15 amp circuits. I would only run 20 amp.

I bet you wouldn't have a problem if you didn't have the 15's.