Let's start with the basics here, I finally managed to acquire a copy of Sims 4 (the premium edition was harder to come by as some retailers only carried a few or thy ran out've stock online. I ended up going with Amazon and my order shipped within a couple of days even though I was told it could take up to 10). Also, mods have been coming out at an alarming frequency and CC is not far behind, as Sims 4 CC is now easier than ever to create yourself!
If you can get your hands on Sims 4 Studio. it's fully integrated with Blender (no more Milkshape) which is completely free to download. No trial, no expiry date, no worries!
That's where my own plans come into play. I have plans to start producing my own Sims 4 content, and now that there's a tool that plays nice with Blender, I can! Other than that, I plan on busting out some nice Graphic T-Shirts as you can never get enough of those!
But in the meantime, here are some Sims 4 Studio Tutorials by Youtube user Patrick Toutant! These cover texturing/recolouring and meshing (making your own 3D models).
This tutorial requires the Blender 3D software, found here. Sims 4 Studio can be found here, and there's a support forum along with it.
You'll need a graphics program for editing textures, as well as a plugin for the software you're using.
Photoshop DDS Plugin (Assuming you have a copy of Photoshop)
Gimp Plugin | Gimp
Or alternatively, you can use Paint.net which has native DDS support.
In terms of Sims 3, I'll continue to work my way toward making cc for that game, albeit it'll probably take a bit longer since I'm still looking for the Blender plugin that can handle Sims 3 meshes. I want to avoid Milkshape as much as possible as a 30 day trial really isn't enough for me to wrap my head around most software.