How to create stuff for use in Garry's Mod

Yeah, I was just wondering if someone could teach me how to make things Gmod since I make vids and like to do my own work. Either that or send me a link that tells me how.
By that, I mean I want to make my own maps, skins, SWEPs, etc.

Maps: hammer
skins: Photoshop, vtf edit
sweps: knowlage of lua scripting

And model making you need somekind of 3D modeling program, 3ds Max or Blender for example.

That is alot of things you are trying to learn at once, focus on your favorite topic or catagory and master it.

Well, I really only want to create maps, but later on I want to create models, but that’s not a big deal.

I learnt how to map in about 2 months, With the power of Youtube, Google and Moddb!