Newbie help - deck building

Hello!

I knew of magic, but had issues every time I tried to learn to play. Had friends who learned by getting thier butts handed to them "teach" me by having me use a bad deck, others question every card I played without explaining anything, and anything in-between.

One of my friends wanted some cards for thier birthday so I go to a local game store and the clerk gave me a couple mono decks (40 card, common & uncommon) and a sheet with basic rules. Said pre-pandemic they used to have "learn to play" nights and would give out these decks of donated cards so people had a base to start from.

This was around the launch of Forgotten Realms, and since I know that setting I started buying cards thinking the D&D stuff I knew would make it easier to learn the game. I was right and between the decks the store gave me and last year's starter set I was able to pick up how to play a basic game. (I still don't know the details of commander, draft, and other formats. I usually only play with my partner so we use precon decks or jumpstarts)

That said...goblin brain like pretty art! I now have boxes of cards everywhere in my house! I have a binder for each set, a fat box for each set (plus a couple more for tokens or artifacts) of "playable cards", with a max of 4 copies per card. Anything beyond 4 is in a box in my closet. Plus quite a few precons & commander decks.

I keep thinking about the gaming store having these decks and have the idea to use my box of surplus to make decks to give to children's hospitals, shelters, or even see if my local store will hold a "learn to play" night...but I don't know how to make a deck!

I've looked. The offical magic video on deck building says to start with a precon and swap out cards...but the only precons in stores are commanders! I found another video "for beginners" and dude rambled about "meta" and didnt explain anything.

What is the opinion of my idea of using my surplus to make decks for new players?

And if people think it's a good idea...how would I go about building these decks? It's going to be common & uncommons (pauper?), and limited to 40 cards so I can make as many decks as possible with my surplus.